As a follow-up to a recent post [LINK], I've been able to somewhat comprehensively catalogue & categorize climates of different population centers roughly in the middle latitudes (23-67 degrees, which are outside of both the tropics and the polar circles) in each continent to understand why certain climate types occur in certain continents and not others. This post explains that further. Again, I am not a trained climatologist or meteorologist; I can't guarantee that this information is accurate, and I can only say that my intuitions seem through my limited understanding to align with superficial aspects of more detailed explanations.
For the rest of this post, I will use the modification of the Trewartha categorization that I explained in the recent post. Each climate label in this categorization has four letters, with the first being uppercase and the remaining 3 being lowercase.
Climate categorization definitions
First letter
The first letter can be A, B, C, D, E, or F. Climate types have the first letter F (polar) if if the mean temperature of the hottest month is less than 10 degrees Celsius. Climate types with the first letter B (semi-arid or arid) are defined based on precipitation thresholds regardless of mean temperatures each month; this will be explained soon. If a climate type does not meet a precipitation threshold for the first letter B, then the first letter is A (tropical) if the mean temperature of the coldest month is at least 18 degrees Celsius, C (subtropical) if the mean temperature of the coldest month is less than 18 degrees Celsius but 8-12 months in the year have a mean temperature of at least 10 degrees Celsius, D (intermediate) if 4-7 months in the year have a mean temperature of at least
10 degrees Celsius (which means the mean temperature of the remaining 5-8 months, including the coldest month, must be less than 10 degrees Celsius), or E (subpolar) if 1-3 months in the year have a mean temperature of at least
10 degrees Celsius (which means the mean temperature of the remaining 9 to 11 months, including the coldest month, must be less than 10 degrees
Celsius). These conditions are the same as in the Trewartha categorization.
The precipitation threshold for climates with the first letter B is \( H = 10(T - 10) + 300S \), where \( T \) is the mean annual temperature in degrees Celsius and \( S \) is the fraction (between 0 and 1) of yearly precipitation that occurs in the summer half of the year (inclusively between April through September in the northern hemisphere, or October through March in the southern hemisphere). These conditions are the same as in the Trewartha categorization.
If the mean temperature of the hottest month is less than 10 degrees Celsius, then the climate type automatically has the first letter F (polar). This holds even if the climate type would otherwise qualify for the first letter B (arid or semi-arid), because close enough to the pole, the air is too cold to hold much moisture anyway, and features of the vegetation are more influenced by the coldness than the dryness per se; more precisely, as a climate becomes colder, less moisture from the ground is lost to evapotranspiration, so the amount of precipitation needed per year to avoid a climate type with the first letter B (arid or semi-arid) is lessened anyway. If a climate type does not qualify for the first letter F (polar) but the yearly precipitation is \( P \leq 2H \), then the climate type has the first letter B (arid or semi-arid); otherwise, the first letter must be A (tropical), C (subtropical), D (intermediate), or E (subpolar) depending on the mean temperatures of the hottest and coldest months and the number of months with mean temperatures of at least 10 degrees Celsius. These conditions are the same as in the Trewartha categorization.
Second letter
The second letter depends on the first letter. If the first letter is B (arid or semi-arid), then the second letter denotes whether the climate is either semi-arid or arid. A semi-arid (steppe) climate, with the second letter being 's', has \( H < P \leq 2H \). An arid (desert) climate, with the second letter being 'w', has \( P \leq H \). These conditions are the same as in the Trewartha categorization.
If the first letter is A (tropical), then the second letter denotes whether the climate is a tropical rainforest climate or a tropical wet-and-dry climate. If at least 10 months each have at least 60 millimeters of precipitation, then the second letter is 'r' (tropical rainforest climate). Otherwise, the climate is a tropical wet-and-dry climate; the second letter is 'w' if the dry season is during the winter half of the year or 's' if the dry season is during the summer half of the year. These conditions are the same as in the Trewartha categorization.
If the first letter is F (polar), then the second letter denotes whether the climate is a tundra climate or an ice cap climate. If the mean temperature of the hottest month is at least 0 degrees Celsius but below 10 degrees Celsius, then the second letter is 't' (tundra climate); otherwise, as every month has a mean temperature below 0 degrees Celsius (implying permanent ice where water is present), the second letter is 'i' (ice cap climate). These conditions are the same as in the Trewartha categorization.
If the first letter is C (subtropical), D (intermediate), or E (subpolar), then the second letter denotes whether the climate has a dry summer or generally uniform precipitation through the year, as dry summers indicate vulnerability to droughts, wildfires, and related natural disasters. This is the main way that my modification differs from the original Trewartha categorization. If all of the following conditions hold, namely that the driest month is in the summer half of the year, the wettest month is in the winter half of the year, the wettest month has at least 3 times the mean precipitation as the driest month, and the summer half of the year has at least 3 months where the mean precipitation is at most 40 millimeters (including the driest month, by definition), then the second letter is 's', indicating a dry summer. Otherwise, the second letter is 'f', indicating a humid summer. Unlike the Köppen categorization, neither the Trewartha categorization nor my modification to it allow for the second letter to be 'w', which would indicate dry winters, when the first letter is C (subtropical), D (intermediate), or E (subpolar), and this is for two related reasons. First, there is no particular climactic or ecological feature unique to places with dry winters, as the dryness corresponds to the time of the year with the least amount of sunlight and the lowest temperatures; this is unlike when the second letter is 's' (dry summer), because dryness in the summer allows for temperatures to become arbitrarily high in the absence of precipitation (even if average temperatures are somewhat more moderate, as may happen when moisture comes in other forms like fog), which can easily lead to wildfires as is characteristic of places that have climate types with the second letter 's' (dry summer). Second, the threshold \( H \) for precipitation for a climate type to have the first letter B (arid or semi-arid) is defined to depend not only on the average temperature for the year but also on the percentage of precipitation in the summer half of the year, because evapotranspiration rates increase as the temperature increases. This means that for two places that have the same average temperature for the year, the one that has a greater percentage of precipitation occurring in the summer half of the year will experience more evapotranspiration because the temperatures in that half of the year are higher, so the climate type there is more likely to have the first letter B (arid or semi-arid) under the Trewartha categorization or my modification of it even if the Köppen categorization would make the first letter C (subtropical) or D (continental) with the second letter 'w' (dry winter), because that becomes the more salient feature of such a climate; if the climate type doesn't have the first letter B (arid or semi-arid), then there is less of a salient difference in the climates & ecologies of areas with climate types with the first letter C (subtropical), D (intermediate), or E (subpolar) and the second letter 'f' (humid summer) whether the winter is dry or not.
Third and fourth letters
The third and fourth letters are more needed in my modification of the Trewartha categorization for comparison of different climates to make sense, but the actual letters are the same (although at or below 0 degrees Celsius, I may have shifted things by 0.1 degree Celsius). In particular, the third letter indicates the mean temperature of the hottest month and the fourth letter indicates the mean temperature of the coldest month. Both the third and fourth letters come from the following set of letters. These letters are 'i' for temperatures of at least 35 degrees Celsius, 'h' for temperatures of at least 28 degrees Celsius but less than 35 degrees Celsius, 'a' for temperatures of at least 22.2 degrees Celsius but less than 28 degrees Celsius, 'b' for temperatures of at least 18 degrees Celsius but less than 22.2 degrees Celsius, 'l' for temperatures of at least 10 degrees Celsius but less than 18 degrees Celsius, 'k' for temperatures of at least 0 degrees Celsius but less than 10 degrees Celsius, 'o' for temperatures of at least -10 degrees Celsius but less than 0 degrees Celsius, 'c' for temperatures of at least -25 degrees Celsius but less than -10 degrees Celsius, 'd' for temperatures of at least -40 degrees Celsius but less than -25 degrees Celsius, and 'e' for temperatures less than -40 degrees Celsius. Thus, when I speak of the temperature-indicative third or fourth letters being higher or lower when comparing two climate types, such statements refer to this temperature scale.
Effects of mountains
Frequently, when considering transitions between climate types, I will refer to mountains lying in some direction relative to an area with a climate type and not further discuss the climate types on or across those mountains. Mountains have their own, typically polar-like, climate types and significantly break up continuity between otherwise geographically adjacent climate types in a given continent. In particular, as I discussed in a previous post [LINK], a mountain range that lies roughly along a line of longitude (meridian) creates a significant rain shadow that will depend on the direction of the prevailing winds; at more tropical latitudes, the prevailing winds are the trade winds going from east to west, so areas east of a mountain will get much more precipitation than areas west of a mountain, while at middle latitudes, the prevailing winds are the prevailing westerlies going from west to east, so areas west of a mountain will get much more precipitation than areas east of a mountain. A mountain range that lies roughly along a line of latitude usually will not create a significant rain shadow unless there is a specific warm ocean current driving wind from the equator to a pole roughly along a line of longitude (meridian), but it will block warm air going from the equator toward a pole and cold air going from a pole toward the equator; thus, it is more likely to create sharper transitions in temperature profiles (third & fourth letters in the climate type), and if this affects the position of the subtropical ridge especially around the west coast of a continent, then it can further create sharper transitions between precipitation profiles based on whether summers are dry.
Follow the jump to see further discussion of actual climate type occurrences. I will focus mostly on climates with the first letter being C (subtropical), D (intermediate), or E (subpolar), as those are the most common in the middle latitudes; there will be some discussion of climates with the first letter being B (arid or semi-arid), as there are many areas in middle latitudes that have semi-arid or arid climates, and there will be brief discussion of climates with the first letter being A (tropical) or F (polar), as those are rare outside of the tropical or polar regions respectively. I should note that this post contains two large biases in sampling. First, I have only considered population centers that are clear on Google Maps. Therefore, some of these climates may actually be more widespread in area than they look based only on where people live. Second, as I'm most familiar with North America, I may have picked more small or mid-sized cities in North America compared to other continents. Therefore, some of these climates may actually be more widespread in other continents than this post may seem to suggest.
Climate types and transitions
Cfhl/Cfhk
I could find climates labeled Cfhl in the latitude range of 24.14-33.69 degrees and Cfhk in the latitude range of 26.89-36.13 degrees, almost exclusively in Taiwan, Japan, the southeastern US, and the coast of China; three exceptions are Lahore, at latitude 31.55 degrees, and Islamabad, at latitude 33.69 degrees and at a moderate elevation above sea level, both in Pakistan, as well as Lucknow, at latitude 26.85 degrees, in India. In particular, the climate transitions from Cfhl in Taiwan and along the coast of China in the latitude range of 24.14-26.07 degrees to Cfhk in the coastal and interior parts of China in the latitude range of 26.89-32.06 degrees, and the climate type Cfhk is present in Japan in the latitude range of 32.80-35.18 degrees. The climate transitions in the southeastern US from Cfhl closer to the coast in the latitude range of 27.52-32.08 degrees to Cfhk in the interior in the latitude range of 32.36-36.13 degrees.
The fact that these climates occur closer to the equator in China could be explained by the influence of the semi-permanent high-pressure system over Lake Baikal in Russia in the winter, creating much more significantly cold and dry weather farther from the equator in China, especially in the interior, compared to similar latitudes in the US. Additionally, warm air in the summer and winter can penetrate the southern US more effectively not just indirectly from the Atlantic Ocean near the east coast of North America (the Gulf Stream) but also more directly moving north from the Gulf of Mexico onto the continent, whereas the geography around China does not favor this sort of transport of warm air. Meanwhile, Japan, being a set of islands, is more directly surrounded by the ocean which is relatively warmer in the winter compared to the continent, so it experiences the Cfhk climate farther from the equator than does China. Thus, it may be fair to say that the Gulf Stream and the Gulf of Mexico make the east coast of North America warmer than the east coast of Asia (in the mainland continent) at similar latitudes.
In Taiwan, the climate type Cfhl is found in the north and west coasts of the island. Most of Taiwan is covered by mountains with only a few small settlements for which I could find climate data, while the south coast is close enough to the equator for the climate type to have the first letter A (tropical). In China, the climate type Cfhl is found along the southern part of the east coast, a bit inland too, and even into the northern parts of Laos & Vietnam, though further inland (in China) toward Kunming, the greater elevation above sea level leads the climate type to transition to Cfbk, while to the north, the climate type transitions to Cfhk. In Lahore, Islamabad, and Lucknow, the climate type Cfhl is mostly surrounded by climate types with the first letter B (arid or semi-arid). Away from the coast of the southeastern US, the climate type Cfhl transitions to the climate type Cfhk inland and to climate types with the first letter B (arid or semi-arid) to the west.
In China, the climate type Cfhk is found to the north and west of the climate type Cfhl, which is farther from the equator or more inland. Apart from transitioning to the climate type Cfhl in the opposite directions, the climate type Cfhk transitions to the climate type Cfak further to the north. In Japan, the climate type Cfhk transitions to the climate type Cfak further to the north along each coast; much of Japan is covered by mountains with only a few small settlements for which I could find climate data. In the more northern or interior parts of the southeastern US, the climate type Cfhk transitions mostly to the climate type Cfak.
These climate types do not exist in Europe because Europe is too far from the equator and does not have an east coast which would touch an ocean transporting warm air & water from the equator. They also do not exist in the continents of the southern hemisphere because there is not enough landmass to warm sufficiently for the hottest month to have the letter 'h'. Essentially, the southern hemisphere is too oceanic. This point will arise again later.
Cfal
This climate type occurs more commonly in the southern hemisphere because of its more oceanic geography. It occurs on the east coast of South America in the latitude range of 23.55-34.88 degrees. It also occurs in Durban, which lies on the east coast of South Africa at a latitude of 29.88 degrees, as well as on the east coast of Australia between Brisbane & Sydney, which span the latitude range of 27.47-33.87 degrees; these latitudes are all elements of the latitude range for this climate type in South America. Essentially, the lesser landmass means that the hottest month cannot be too warm, and the greater presence of the ocean means that the coldest month cannot be too cold even if polar air masses (from Antarctica) make incursions into the continent; plus, Durban is close to the southernmost point of Africa, so there is a lot more ocean separating that continent from the pole.
In South America, the climate type Cfal transitions to the climate type Cfak to the south (closer to the pole), climate types with the first letter A (tropical) to the north (closer to the equator), and climate types with the first letter B (arid or semi-arid) to the west. From the east coast of South Africa, the climate type Cfal transitions to the climate type Cfbl along the south coast of South Africa, the climate type Cfbk in the elevated areas a little further inland relative to Durban, and climate types with the first letter A (tropical) into the coast of Mozambique. From the central part of the east coast of Australia, the climate type Cfal transitions to the climate type Cfbl to the south & east toward the southern part of the east coast of Australia, climate types with the first letter A (tropical) toward the northern part of the east coast of Australia, the climate type Cfak to the southwest (inland), and climate types with the first letter B (arid or semi-arid) to the west (inland).
In the northern hemisphere, this climate type is restricted to Kathmandu at a latitude of 27.72 degrees (which is still within the aforementioned latitude ranges) due to its elevation as well as the more eastern parts of a couple of the islands of the Azores in the Atlantic Ocean in the latitude range of 38.66-39.44 degrees; this climate type arises farther from the equator in the Azores due to the warmth of the water from the Gulf Stream. Otherwise, North America and Eurasia have too much landmass to support this climate type where hottest month is warm but the difference in temperature between the hottest and coldest months is not too big.
Cfak
This climate type is much more common in the northern hemisphere compared to the climate type Cfal. The climate type Cfak occurs in the overall latitude range of 30.66-45.65 degrees. In particular, it occurs in the interior of the southeastern US in the latitude range of 32.30-36.85 degrees, in Chengdu in the interior of China at a latitude of 30.66 degrees with a slight elevation above sea level, in Yancheng along the coast of China at a latitude of 33.35 degrees, in Zhengzhou in the interior of China at a latitude of 34.76 degrees with a slight elevation above sea level, in the Korean Peninsula in the latitude range of 35.16-36.03 degrees, in Tokyo in Japan at a latitude of 35.69 degrees, in southeastern Australia around a latitude of 36 degrees, in Niigata in Japan at a latitude of 37.92 degrees, in Dushanbe in Tajikistan at a latitude of 38.54 degrees with a moderate elevation above sea level, in Bahía Blanca in Argentina at a latitude of 38.72 degrees, and in Europe in the latitude range of 40.64-45.65 degrees. In Europe, it occurs in many cities on the coast of the Balkan Peninsula along the Adriatic Sea as well as Pescara on the coast of the Adriatic Sea in Italy, along the west coast of Italy strictly north of Rome (not including Rome), between Marseille & Avignon as well as around Toulouse in France, around Thessaloniki on the coast of the Aegean Sea in Greece, around İstanbul between the Aegean & Black Seas in Turkey, and in the cities along the coast of the southern part of the Black Sea (not far from Turkey in general, though far from İstanbul in particular).
Explanations for why this climate type occurs at the latitudes it does for each continent, and why this climate type does not occur for some continents, are the same as for the Cfhl/Cfhk climate types for North America, Asia, and Africa. However, its occurrence in Europe, South America, and Australia, unlike the Cfhl/Cfhk climate types which do not occur there, deserves more explanation. In particular, in Europe, the combination of the warmth of the Black, Mediterranean, and Adriatic Seas, the warmth of the Gulf Stream flowing from the Atlantic Ocean from the west, and the lesser but still present occasional flows of air from the poles over a lesser landmass compared to North America or Asia creates conditions for moderately cold but not freezing winters, moderately warm but not hot summers, and enough months with a mean temperature above 10 degrees Celsius to be considered subtropical. This is one example of how Europe is warmer than North America or Asia at similar latitudes, even though the existence of this climate type in Europe at all, in the absence of an east coast next to an ocean, is more a quirk of the specific geography of Europe. In South America & Australia, the areas with the climate type Cfak are a bit inland (west) of the respective east coasts at latitudes where warmer waters from the Atlantic or Pacific Oceans, respectively, mix with the cooler (but not so cold) waters of the Antarctic Ocean. As will become clear in later sections, this means that coastal areas of South America & Australia to the south & east of areas with the climate type Cfak typically have the climate types Cfbl or Cfbk, because the ocean currents there are not warm enough for the summers to have temperatures with the third letter being 'a' or higher. Moreover, the cooler ocean waters in those places as well as in Europe (though the Gulf Stream isn't really "cold" per se), compared to the very warm waters of the Gulf of Mexico along the south coast of the southeastern US and of the Gulf Stream in the Atlantic Ocean along the east coast of the US, along with the restriction of the climate type Cfak in Europe, South America, and Australia to more inland areas of those continents, means that areas with the climate type Cfak are much drier in Europe, South America, and Australia than in North America.
In the southeastern US, the climate type Cfak transitions to the climate type Dfak to the north, the climate type Cfhk to the south, and climate types with the first letter B (arid or semi-arid) to the west. In China, the climate type Cfak transitions to the climate type Dfak to the north, the climate type Cfhk to the south, and climate types with the first letter B (arid or semi-arid) to the west. In the Korean Peninsula, the climate type Cfak transitions to the climate type Dfak to the north along the east coast and to the climate type Dfao to the north along the west coast (due to the mountainous geography of the interior of South Korea along with the bays on each side creating interesting rain shadow effects and different precipitation patterns). In Japan, the climate type Cfak transitions to the climate type Dfak to the north and the climate type Cfhk to the south. Dushanbe in Tajikistan is in a mountainous area in the deep interior of Asia, so it does not make as much sense to consider continuous transitions in climate type, especially as the nearest major cities (for which I could easily find reliable climate data that is easy to read) are quite far away; additionally, it has the climate type Cfak only because the wettest month happens to be in the beginning of the summer half of the year, but otherwise, it should have a climate type like Csak because its summers are much drier than its winters. In southeastern Australia, the climate type Cfak transitions to the climate type Cfbk to the south, the climate type Cfal to the east & north, and climate types with the first letter B (arid or semi-arid) to the west. In South America, the climate type Cfak transitions to the climate type Cfal to the north, the climate type Cfbk to the southeast, and climate types with the first letter B (arid or semi-arid) to the west. In the cities along the coast of the Balkan Peninsula along the Adriatic Sea, the climate type Cfak transitions to the east (inland) to the climate types Dfak in the lowlands and Dfbk in the highlands. From Pescara in Italy along the Adriatic Sea, the climate type Cfak transitions to the climate type Csak to the south and Dfak to the north, while the Apennine Mountains lie to the west; the former indicates the peculiar conditions of the Adriatic Sea giving way to the more dominant combined effects of the subtropical ridge, the warmth of the Mediterranean Sea, and the Gulf Stream from the Atlantic Ocean yielding drier summers. From the northwest coast of Italy along the Mediterranean Sea, the climate type Cfak transitions to the climate type Csak to the north and south, while the Apennine Mountains lie to the east; this section of Italy happens to have the climate type Cfak instead of Csak too because it is prone to summer thunderstorms along a peculiar particular low-pressure track. Marseille & Avignon in France only happen to have the climate type Cfak because its wettest month happens to be in September, which is at the end of the summer half of the year, even though they would otherwise qualify for the climate type Csak and Marseille is surrounded by cities on either side of it along the coast of the Mediterranean Sea with climate type Csak; areas to the north of Avignon have the climate type Dfak. From Toulouse in France, the climate type Cfak transitions to the climate type Dfak to the north and the climate type Cfbk to the northwest (closer to the Atlantic Ocean with the moderating influence of the Gulf Stream), while the Pyrenees Mountains lie to the south. From Thessaloniki in Greece, the climate type Cfak transitions to the climate type Dfak to the northwest (inland) and the climate type Csak along the coast of the Mediterranean Sea, although Thessaloniki itself has somewhat drier summers than winters (in contrast to most other places listed here with the climate type Cfak). İstanbul in Turkey has the climate type Cfak mainly because despite the facts that the driest months are in the summer half of the year, the wettest months are in the winter half of the year, and the wettest month has more than 3 times as much precipitation as the driest month, the third driest month in the winter half of the year has just over 40 millimeters of precipitation; the climate type Cfak transitions to the climate type Csak to the west and the climate type Dfak to the east. İstanbul is part of a surprisingly big area in Turkey with the climate type Cfak despite being relatively dry, only because the temperatures are moderate enough and a relatively wet month in the summer half of the year is followed by a few dry months (all due to the higher elevations of these cities), which transition to the the climate types Csak or Dsak to the west & south and the climate type Dfak to the east. The cities along the coast of the southern part of the Black Sea have the climate type Cfak transition to the climate type Dfak north along the coast of either side of the Black Sea or inland in any direction.
It is worth explaining further how even though all of these places have
the climate type Cfak, the climates still have important differences. Most of these places, except those in the rain shadow of a mountain range, get more an average of than 1,000 millimeters of precipitation per year, but the distribution of precipitation across the year differs. In North America, around Bahía Blanca in South America, and in the cities to the southwest of the Black Sea in Europe, precipitation is largely uniformly distributed, but North America gets much more precipitation due to the Gulf of Mexico & Gulf Stream in the Atlantic Ocean combined with some of these places being on the windward side of (relatively short) mountains, whereas Bahía Blanca gets colder water from the Atlantic Ocean in the southern hemisphere despite being directly on the ocean, and the cities to the southwest of the Black Sea in Europe are much closer to the pole (so the colder air has a lower equilibrium partial pressure of water) and on the leeward side of mountains relative to the prevailing westerlies (which would carry milder moist air over the Gulf Stream in the Atlantic Ocean). In Asia, winters are much drier than summers due to the area of high pressure over Lake Baikal in Russia in the winter. Around the Adriatic Sea & Aegean Sea in Eurasia, summers are a bit drier than winters due to the overall influence of being on the western side of the continent facing prevailing westerlies & the Gulf Stream in the Atlantic Ocean; cities to the southeast of the Black Sea in Europe exhibit this effect too, as the Black Sea is essentially a miniature ocean. In France, the cities of Marseille, Avignon, and Toulouse all get averages of less than 700 millimeters of precipitation per year due to the proximity to the subtropical ridge in the summer half of the year, and this leads to a slightly drier summer in Marseille, though the precipitation distribution is more uniform in Avignon and toward a slightly drier winter in Toulouse as those cities are farther from the influence of the subtropical ridge near the Mediterranean Sea & more in line with the influence of the Gulf Stream in the Atlantic Ocean.
It is uncommon for the climate type Cfak to transition to the climate type Cfbk. I could only see it in Bahía Blanca & La Plata in Argentina going to the southeast, in southeastern Australia going to the south, and in Toulouse in France going to the northwest. In all cases, those directions are toward the moderating influence of the ocean, which at those latitudes happens to be a bit cooler (even for areas along the east coast of the corresponding continent, while in France which is on the west coast of its continent, the warmth of the Gulf Stream is mitigated by the much higher latitude there). Additionally, the climate type Cfak only transitions to the climate type Csak specifically around the northern & eastern parts of the Mediterranean Sea due to the peculiar combinations of mountains, highlands, moderate landmasses, the Gulf Stream from the Atlantic Ocean, and the subtropical ridge in the summer extending from the Azores to the east. Usually, the climate type Cfak transitions to the climate type Cfhk closer to the equator or the climate type Dfak further from the equator or in a highland.
Cfbl
Like the climate type Cfal and for similar reasons, the climate type Cfbl occurs almost exclusively in the southern hemisphere because of its more oceanic geography. It occurs on the east coast of South America in the latitude range of 24.78-25.43 degrees, on the south coast of South Africa in the latitude range of 33.02-33.96 degrees, around Batemans Bay on the southern part of the east coast of Australia at a latitude of 35.71 degrees, and around Auckland in the northern part of New Zealand (closer to the equator) at a latitude of 36.84 degrees.
In South America, the climate type Cfbl occurs in Curitiba and Ponta Grossa in Brazil and in Salta in Argentina, all of which are at moderate elevation above sea level. Thus, around Curitiba and Ponta Grossa in Brazil, the elevation decreases in all directions, so the climate type Cfbl transitions to the climate type Cfal, while in Salta in Argentina, the climate type Cfbl transitions to climate types with the first letter B (arid or semi-arid) in all directions because those are lowlands affected by the rain shadow (relative to the prevailing westerly winds at those latitudes) of the Andes Mountains along with the subtropical ridge that frequently arises at those latitudes. In South Africa, the climate type Cfbl transitions to the climate type Cfal to the east along the south coast, the climate type Csbl to the west along the south coast, and to the climate type Cfbk to the north (inland) where highlands prevail. In Australia, the climate type Cfbl transitions to the climate type Cfal to the north (closer to the equator) along the east coast and the climate type Cfbk to the south (closer to the pole) along the east coast toward the south coast. In New Zealand, the climate type Cfbl transitions to the climate type Cfbk to the south (closer to the pole).
It is worth explaining further how even though all of these places have the climate type Cfbl, the climates still have important differences. Almost all of these places get an average of at least 700 millimeters of precipitation per year, but the distribution through the year is different. Salta in Argentina, Ponta Grossa & Curitiba in Brazil, Mbabane in Eswatini & East London in South Africa, and Batemans Bay in Australia all lie on their respective countries' east coasts, so the winters are drier than the summers; this effect is more pronounced for Salta in Argentina, Ponta Grossa & Curitiba in Brazil, and Mbabane in Eswatini as they are more inland & elevated. Gqeberha in South Africa exhibits a continuous transition in the climate type Cfal between the climate type Cfal around Durban on the east coast of South Africa and the climate type Csbl around Cape Town on the west coast of South Africa, so it has a slightly drier winter. Auckland in New Zealand gets an average of more than 1,200 millimeters of precipitation per year, but it has a slightly drier summer even though New Zealand is to the east of Australia, because it is close enough to the pole that the oceanic effects are dominated by the milder Antarctic Ocean rather than the warmer Pacific Ocean; perhaps the mildness of the Antarctic Ocean, like the mildness of most oceans along the west coasts of most continents, leads to higher pressure that can support an unusual (compared to other continents) subtropical ridge to the east of Australia.
Cfbk
Unlike the climate types Cfal & Cfbl, the climate type Cfbk is not restricted to one hemisphere. However, with respect to continents and within the continents where the climate type Cfbk is present, the climate type Cfbk is much less widespread. In particular, it is restricted to Kunming in China at a latitude of 25.05 degrees, Johannesburg in South Africa at a latitude of 26.20 degrees, Melbourne in Australia at a latitude of 37.81 degrees, Mar del Plata in Argentina at a latitude of 38.00 degrees, Wellington in New Zealand at a latitude of 41.29 degrees, and the cities along the west coast of Europe next to the Atlantic Ocean between Braga in Portugal and La Rochelle in France (including the west & north coasts of Spain) with a latitude range of 41.55-46.16 degrees.
The climate type Cfbk arises in Kunming & Johannesburg at lower latitudes due to higher elevations above sea level. From Kunming in China, the climate type Cfbk transitions to the climate type transitions to the climate type Cfak in all directions. From Johannesburg in South Africa, the climate type Cfbk transitions to the climate type Cfak to the east, the climate type Cfbl to the south, and climate types with the first letter B (arid or semi-arid) to the west.
The climate type Cfbk arises in Melbourne in Australia, Wellington in New Zealand, and the coastal part of Europe along the Atlantic Ocean between Braga in Portugal and La Rochelle in France because of the stronger oceanic influence. In the former two cases, the Antarctic Ocean consistently moderates the temperatures, while in the latter group, the Gulf Stream in the Atlantic Ocean ensures moderate temperatures & wet conditions. From Melbourne in Australia, the climate type Cfbk transitions to the climate type Cfbl to the north, the climate type Csbk to the west, and the climate type Cflk to the south (hopping across the Bass Strait to the island of Tasmania in Australia). From Wellington in New Zealand, the climate type Cfbk transitions to the climate type Cfbl to the north and the climate type Dfbk to the south. From the coastal part of Europe between Braga in Portugal and La Rochelle in France, the climate type Cfbk transitions to the climate type Dfbk to the north in France, the climate type Cfak to the east in France, and the climate type Csbk to the south in Portugal, while to the south in Spain lie the Cantabrian Mountains running from west to east.
From Mar del Plata in Argentina (which is on the east coast along the Atlantic Ocean), the climate type Cfbk transitions to the climate type Cfak in all directions inland. Thus, although Mar del Plata lying along the east coast of Argentina should suggest a third letter higher than 'b' especially when inland locations at the same latitude have the climate type Cfak, the lack of something like the Gulf Stream in the southern hemisphere (despite still being the Atlantic Ocean) means that the Atlantic Ocean at those latitudes is cooler especially with mixing of water from the Antarctic Ocean, and the inland locations that have the climate type Cfak have warmer summers more because of the drier continental influence than because of any putative warm ocean (as would be the case in North America).
It is worth explaining further how even though all of these places have the climate type Cfbk, the climates still have important differences. Kunming in China & Johannesburg in South Africa are inland, elevated, and closer to their respective countries' east coasts, so the winter is much drier than the summer; this effect is similar but lessened in Mar del Plata, which is on the east coast of Argentina, so the winter is slightly drier than the summer. In any case, all of these cities get an average of between 700-1,000 millimeters of precipitation per year, because while the warm ocean waters near the east coasts should bring a lot of moisture, this is mitigated the inland locations and the lesser predictability of prevailing winds. Canberra & Melbourne in Australia are also near the southeast coast of Australia, with Canberra being a bit more inland, so the milder waters of the Antarctic Ocean dominate even as they mix a bit with the warmer waters of the Pacific Ocean, ensuring slightly drier winters with 500-600 millimeters of precipitation per year. By contrast, the cities between Braga in Portugal & Santander in Spain are on the west coast of Europe along the Atlantic Ocean, so the combination of the predictable winds in the form of the prevailing westerlies coming from the Atlantic Ocean as well as the relative warmth (for those latitudes) of the Gulf Stream in the Atlantic Ocean ensure much drier summers (though not dry enough for the climate type to be Csbk or something similar) and precipitation levels of more than 1,000 millimeters per year; this effect is mitigated when going to Bordeaux & La Rochelle in France, because while those are also on the west coast of France on the Atlantic Ocean, they are closer to the pole, so perhaps the migration of the subtropical ridge to those latitudes in the summer, as evinced by the slightly drier summers, along with the colder air in the winter having a lower equilibrium partial pressure of water explains why the precipitation level is on average less than 1,000 millimeters per year. Wellington in New Zealand follows a similar pattern as the cities between Braga in Portugal & Santander in Spain, with a slightly drier summer and with an average of more than 1,000 millimeters of precipitation per year, even though New Zealand is to the east of Australia, perhaps for similar reasons as Auckland in New Zealand with the climate type Cfbl & being to the east of Australia having slightly drier summers.
The climate type Cfbk does not exist in North America. This is because on the eastern side of the US where the climate type Cfak exists, going closer to the pole brings more of a continental influence due to the greater landmass closer to the pole, such that summers are still hot with the third letter being 'a' due to the land heating up more but there are enough incursions of air from the pole at other times of the year that fewer than 8 months have mean temperatures of at least 10 degrees Celsius; thus, the climate type Cfak transitions to the climate type Dfak instead of the climate type Cfbk. Along the west coast where the climate type Csbk exists, there are too many mountains to allow smooth transitions of climate types, and in any case, closer to the pole, the Pacific Ocean is too cold and there are too many continental influences for an area to have a climate with at least 8 months having mean temperatures of at least 10 degrees Celsius and dry summers.
Cfll/Cflk
I could not find the climate type Cfll in any human settlements. This does not mean that it doesn't exist; it might only exist in places with no permanent human population, and those could be relatively large areas. However, if it turns out that there are no places with the climate type Cfll, then it could be worth exploring why that is. It is worth noting that the climate type Csll does exist in a handful of places. This would suggest that to have summer and winter temperatures be so similar to each other, there needs to be a drying trend in the summer such that cool summer temperatures are achieved through fog but not precipitation per se (as is the case for San Francisco in the US); the combination of sufficient precipitation in the summer and a relatively small difference between summer & winter temperatures may imply that the location is too close to the pole for the fourth letter to be 'l'.
The climate type Cflk is rare and restricted to locations with significant oceanic influences. I could only find three such locations, two of which are in the southern hemisphere. One in the southern hemisphere is around Temuco in Chile at latitude 38.73 degrees; from there, the climate type Cflk transitions to the climate types Csll/Cslk to the north, as one month in the summer half of the year is marginally too wet for the climate type to be Cslk, and the climate type Dflk to the south, while the Andes Mountains lie to the east. There, the Coast Range of Chile is low enough in height/elevation for moderately cool moist westerly air to dump enough rain at a moderately high latitude there that temperatures are always mild to cool through the year. The other in the southern hemisphere is around the lowlands of the island of Tasmania in Australia (for which the latitude of Hobart in Australia is 42.88 degrees); from there, the climate type Cflk transitions to the climate type Cfbk (hopping across the Bass Strait to the mainland of Australia). The only instance of the climate type Cflk in the northern hemisphere is in North America around the city of Denmark on the west coast of Oregon in the US at a latitude of 42.89 degrees; from there, the climate type Cflk transitions to the climate type Cslk in both directions along the coast because the climate type Cflk only exists in that location due to one month in the summer half of the year having marginally too much rain to qualify as the climate type Cslk, while mountains lie to the east. Otherwise, in the northern hemisphere, continental influences ensure that even on the west coasts, there are too few months with mean temperatures of at least 10 degrees Celsius and too many ways for the hottest month of the year to have a higher mean temperature (which is why in those places, the climate type Cfbk is more likely to transition to the climate type Dfbk instead of the climate type Cflk toward the pole in the northern hemisphere).
Cshl/Cshk
I could find the climate types Cshl/Cshk in Antalya, İzmir, Athens, Haifa, and Seville in Eurasia, spanning the latitude range of 32.82-38.42 degrees (although this encompasses many cities along many different parts of the Mediterranean Sea) and in Fresno & Redding in the Central Valley of California in the US at the respective latitudes of 36.75 degrees & 40.58 degrees. I do not distinguish between these two climate types because the areas with the climate type Cshk have coldest mean monthly temperatures that are marginally below the threshold for the climate type Cshl. It is important to note that although multiple cities in the Central Valley of California in the US have the climate types Cshl/Cshk, they do not span a latitude range, because as I will explain in later sections, cities at intermediate latitudes in the Central Valley of California in the US have different climate types due to the peculiar geography there.
Within the Central Valley of California in the US, from Fresno toward the northwest and from Redding toward the southeast, the climate types Cshl/Cshk transition to the climate type Csak; this is because of the Sacramento River and the corresponding opening in the Coast Range of California letting in cooler air from the west (the Pacific Ocean) in the summer; both Fresno & Redding are surrounded by mountains to the west & east, Redding is also surrounded by mountains to the north, and the climate types Cshl/Cshk from Fresno transition to climate types with the first letter B (arid or semi-arid) to the southeast (still within the Central Valley of California in the US). From Seville in Spain, the climate types Cshl/Cshk transition to the climate type Csal to the south & west (toward the coast of the Mediterranean Sea, especially closer to the Atlantic Ocean) and to climate types with the first letter B (arid or semi-arid) to the north & east (inland). From Haifa in Israel, the climate types Cshl/Cshk transition to the climate type Csal to the north & south along the coast of the Mediterranean Sea and to the climate type Csak to the east (inland). From Antalya & İzmir in Turkey, the climate types Cshl/Cshk transition to the climate type Csak to the north & east (inland). From Athens in Greece, the climate types Cshl/Cshk transition to the climate type Csak to the north; Athens is otherwise largely surrounded by mountains.
I could not find the climate types Cshl/Cshk in South America, Africa, or Australia. In South America, especially in Chile, the transition from climate types with the first letter B (arid or semi-arid) closer to the equator to climate types types with the first letter C (subtropical) & second letter 's' is broken up by mountains; a similar effect, though lesser in magnitude, arises in the western part of South Africa. In those continents, places that have dry summers but wet winters are cooled enough that the third letter must be below 'h'. In Australia, there are very few cities with climate data that I could find on Wikipedia, but I could find it more plausible there that the climate types Cshl/Cshk occur as transitions from the climate types Csal/Csak near the west coast of Australia to climate types with the first letter B (arid or semi-arid) to the east & north (inland).
Csal
I could find the climate type Csal along the southern part of the west coast of Australia (especially around Perth) and to the north (slightly inland) of the western & central parts of the south coast of Australia (especially around Adelaide) around the latitude range of 32-35 degrees, around Tel Aviv in Israel & Beirut in Lebanon around the latitude range of 32-34 degrees, along the western & central parts of the north coast of Africa in the latitude range of 32.89-36.80 degrees, around Palermo in Italy (near the middle of the Mediterranean Sea, close to the central part of the north coast of Africa) at a latitude of 38.11 degrees, along the south coast & southern part of the west coast of Portugal in the latitude range of 37.02-38.73 degrees, around the northern part of the east coast of Spain in the latitude range of 39.47-41.38 degrees, around Vlorë in Albania on the coast of the southern part of the Adriatic Sea at a latitude of 40.47 degrees, on Santa Maria Island of the Azores in Portugal at a latitude of 36.97 degrees, around El Cajon slightly inland of San Diego in the US at a latitude of 32.80 degrees, and in the Greater Los Angeles area in the US (along the southern part of the coast there and somewhat inland) in a latitude range of 33.67-34.18 degrees. It is important to note that mountains break up the continuity of climate types between El Cajon & the Greater Los Angeles area in the US.
From El Cajon as well as from the Greater Los Angeles area in the US, the climate type Csal transitions to the climate type Csbl to the west & southwest (toward the west coast along the Pacific Ocean) and to climate types with the first letter B (arid or semi-arid) to the south & east, while mountains (the Transverse Ranges) lie to the north. In Australia, especially around Perth & Adelaide, the climate type Csal transitions to the climate type Csbl to the south (toward the south coast along the Antarctic Ocean) & east and to climate types with the first letter B (arid or semi-arid) to the north (inland or along the west coast of Australia, potentially first transitioning to the climate types Cshl/Cshk). From Beirut in Lebanon & Tel Aviv in Israel, the climate type Csal transitions to the climate type Csak to the east (inland), the climate types Cshl/Cshk toward their midpoint around Haifa in Israel along the coast of the Mediterranean Sea as well as to the north in Turkey & around Aleppo in Syria, and climate types with the first letter B (arid or semi-arid) to the south (toward the Arabian Desert). Palermo on Sicily in Italy having the climate type Csal is representative of most of the island of Sicily in Italy and the southernmost points of the mainland of Italy, though marginally to the north in the southern part of the mainland of Italy, the climate type Csal transitions to the climate type Csak. Vlorë in Albania is largely surrounded by mountains, so the climate type Csal transitions to the climate type Csak in the nearest major cities in Albania to the north. From the western & central parts of the north coast of Africa (along the Mediterranean Sea), the climate type Csal transitions to the climate type Csak marginally to the south (inland) and then to climate types with the first letter B (arid or semi-arid) further to the south. From the northern part of the east coast of Spain, the climate type Csal transitions to climate types with the first letter B (arid or semi-arid) further to the west (inland) & south. The Azores in Portugal are islands, so it doesn't make sense to talk about transitions from the climate type Csal. From the south coast & southern part of the west coast of the mainland of Portugal, the climate type Csal transitions to the climate types Cshl/Cshk to the east and to the climate type Csbl to the north.
I could not find this climate type in South America for similar reasons as being unable to find the climate types Cshl/Cshk in South America. This is more suggestive that the Pacific Ocean near South America is colder than at similar latitudes near North America, much like how the existence of the climate type Csal in Europe at higher latitudes than in North America (due to the Gulf Stream in the Atlantic Ocean and the greater low-lying landmass of the northern part of Africa, especially the Sahara Desert, to the south that becomes hot in the summer compared to North America) strengthens the claim that Europe is warmer than North America at similar latitudes. Additionally, the fact that I could not find the climate type Csal in South Africa does not mean that it doesn't exist there (as it may exist as a transition region from the climate type Csal to climate types with the first letter B (arid or semi-arid) further inland), merely that I couldn't find the data; however, if it really only exists in the northern part of Africa but not in South Africa, the latter could be because of the combination of lesser landmass, cooler ocean waters, and latitude [in South Africa].
Csak
The places where I could find the climate type Csak in North America, Asia, and Africa tend to be similar to those where I could find the climate type Csal but more inland; in many cases, places where I could find the climate type Csak are more often adjacent to mountains on at least one side (usually in valleys). These include places around Amman in Jordan at a latitude of 31.95 degrees, around Homs in Syria at a latitude of 34.73 degrees, around Fes in Morocco at a latitude of 34.04 degrees, around Paso Robles & Gonzales in California in the US (in the valley of the Salinas River) at latitudes of 35.64 & 36.51 degrees, between Modesto & Paradise in California in the US (in the central part of the Central Valley of California in the US) in the latitude range of 37.66-39.76 degrees, between Cloverdale & Ukiah in California in the US (in the valleys of the Russian River in the US) in the latitude range of 38.80-39.15 degrees, around Shasta Lake in California in the US (at a higher elevation relative to Redding in California in the US, which is the adjacent city to the south) at a latitude of 40.68 degrees, around Málaga in Spain at a latitude of 36.72 degrees, between Castelo Branco in Portugal & Madrid in Spain (roughly along a line of latitude) around a latitude of 40.5 degrees, between Brindisi & Foggia on the east coast of Italy (along the coast of the southern part of the Adriatic Sea) in the latitude range of 40.63-41.46 degrees, between Naples & Rome on the west coast of Italy (along the coast of the Mediterranean Sea) in the latitude range of 40.83-41.89 degrees, and around Montpellier & Nice in France in the latitude range of 43.61-43.70 degrees.
From Amman in Jordan or Homs in Syria, the climate type Csak transitions to the climate type Csal to the west (toward the west coast, along the Mediterranean Sea), the climate types Cshl/Cshk to the north (Syria & Turkey), and climate types with the first letter B (arid or semi-arid) to the south & east. From Fes in Morocco, the climate type Csak transitions to the climate type Csal to the north & west (toward the coasts along the Mediterranean Sea or Atlantic Ocean) and to climate types with the first letter B (arid or semi-arid) to the south & east (inland). Paso Robles in the US is largely surrounded by mountains. From Gonzales in California in the US within the valley of the Salinas River, the climate type Csak transitions to the climate type Csll to the northwest toward Salinas & to the climate type Csbl to the southeast toward Soledad; these are not continuous transitions, perhaps because of microclimates caused by the narrow valley geography, and Gonzales is otherwise surrounded by mountains. From the cities between Modesto & Paradise in California in the US, the climate type Csak transitions to the climate types Cshl/Cshk to the northwest & southeast within the Central Valley of California in the US; they are otherwise surrounded by mountains. The cities between Cloverdale & Ukiah in California in the US are largely surrounded by mountains. Shasta Lake in California in the US is right next to Mount Shasta; the only lowland area is Redding in the US, so the climate type Csak transitions to the climate types Cshl/Cshk to the south. From Málaga in Spain (which is on the south coast, along the Mediterranean Sea), the climate type Csak transitions to the climate types Cshl/Cshk to the north. From the cities between Castelo Branco in Portugal & Madrid in Spain, the climate type Csak transitions to the climate type Csbk to the north, the climate type Csal to the south, and climate types with the first letter B (arid or semi-arid) to the east. From the cities between Brindisi & Foggia in Italy, the climate type Csak transitions to the climate type Cfak to the north along the coast of the Adriatic Sea; mountains lie to the west. From the cities between Naples & Rome in Italy (on the west coast along the Mediterranean Sea), the climate type Csak transitions to the climate type Cfak to the north; mountains lie to the east. Nice in France is surrounded by mountains. From Montpellier in France, the climate type Csak transitions to the climate type Cfak to the southeast toward Marseille and to the northwest toward Toulouse; mountains lie to the southwest.
I could not find the climate type Csak in South America or South Africa for similar reasons as being unable to find the climate types Csal in South America or South Africa. Additionally, I could not find the climate type Csak in Australia, likely because the moderate ocean waters are too warm for the coldest mean monthly temperature to be below 'l' along the west or southwest coast where summers are dry, and the huge hot desert inland means moderation would be harder to find further inland.
Csbl
I could only find the climate type Csbl around Cape Town in South Africa at a latitude of 33.93 degrees, the western (south & southeast of Perth) & central (southwest & south of Adelaide) parts of the south coast of Australia around the latitude range of 33-35 degrees, and various parts of California in the US. In particular, in California in the US, the climate type Csbl occurs on the west coast (along the Pacific Ocean) in its southern part in the latitude range of 32.63-35.27 degrees, between the cities of King City & Soledad in the valley of the Salinas River in a latitude range of 36.22-36.43 degrees, around Santa Cruz at a latitude of 36.97 degrees, and in the cities on the coast along the southern and eastern edges of the San Francisco Bay (between San Jose & Oakland) in the latitude range of 37.34-37.80 degrees.
From Cape Town in South Africa, the climate type Csbl transitions to climate types with the first letter B (arid or semi-arid), perhaps with the climate type Csal as an intermediate step. From the south coast of Australia, the climate type Csbl transitions to the climate type Csal to the north (especially inland but also along the west coast of Australia). From the southern part of the west coast of California in the US, the climate type Csbl transitions to the climate type Csal to the east, while mountains lie to the north & south. The climate type Csbl continues into the central part of the west coast of California in the US and transitions to the climate type Csll to the north, while mountains lie to the east. From the cities between King City & Soledad in the valley of the Salinas River in California in the US, the climate type Csbl transitions to the climate type Csak to the northeast, which is a discontinuous transition due to microclimates caused by the narrow valley geography, while mountains lie on all other sides. From the southern and eastern parts of the San Francisco Bay area in the US, the climate type Csbl transitions to the climate type Csbk toward Los Gatos & Gilroy in the south (after which there are mountains), the climate type Csll toward Richmond in the north (relative to Oakland), the climate type Cslk toward San Francisco in the west (relative to Oakland) across the San Francisco Bay, and the climate type Csbk toward Palo Alto in the north or west (relative respectively to San Jose across land or Fremont across the San Francisco Bay); mountains lie in all directions away from the San Francisco Bay. From Santa Cruz in California in the US, the climate type Csbl transitions to the climate type Csll when following the coast along the Monterey Bay toward the south, while mountains lie in all other directions.
It is worth emphasizing just how mountainous California in the US is through the state, especially outside of the Central Valley. This is why although most parts of California have climate types with the first letter C (subtropical) and the second letter 's' (indicating summers), the third & fourth letters are much more variable, as mountains in all directions create rain shadows as well as stratification in temperatures that break up a lot of continuity in climate types that could otherwise exist as they do in Europe, northern Africa, and western Australia.
I could not find the climate type Csbl in South America or Europe. Its absence from South America is for similar reasons as the absence of the climate type Csal from South America. The absence of the climate type Csbl from Europe is somewhat less intuitive, especially when considering that a strong oceanic influence is needed to create the combination of conditions defining this climate type, namely at least 8 months with mean temperatures of at least 10 degrees Celsius, warm (but not hot) summers & mild (but not cool) winters, and dry summers, and Europe should have this in the form of the Gulf Stream in the Atlantic Ocean. I think the reason is that the Gulf Stream is so warm that areas of Portugal or Spain that might otherwise have the climate type Csbl actually have the climate type Csal, and moving closer to the pole, the latitude is so high and there is enough landmass that the winters become cool (yielding the climate type Csak) before the summers become warm instead of hot (yielding the climate type Csbk, in turn skipping the climate type Csbl).
Csbk
I could find the climate type Csbk in different parts of Chile, California in the US, and Portugal. In particular, in Chile, I could find it in the cities of the Central Valley between Santiago & Traiguén in the latitude range of 33.45-38.25 degrees (at moderate elevation at least for the cities between Santiago & Rancagua). In California in the US, I could find it in the cities immediately to the south, southeast, and northwest of San Jose in the latitude range of 37.01-37.43 degrees, in the cities of the Napa Valley between Napa & Yountville in the latitude range of 38.29-38.41 degrees, in the cities of the Sonoma Valley in the latitude range of 38.25-38.46 degrees, and in the cities between Petaluma & Healdsburg in the latitude range of 38.23-38.63 degrees. In Portugal, I could find it between the cities of Coimbra & Porto in the latitude range of 40.21-41.16 degrees.
From the cities in Chile between Santiago & Traiguén, the climate type Csbk transitions to the climate type Cslk to the west (on the west coast along the Pacific Ocean) and the climate type Cflk toward Temuco to the south; Santiago is surrounded by mountains in all directions except the south, and cities to its south are surrounded by mountains to the east & west, though the Coast Range of Chile to the west is short enough to the west of cities between Curico & Los Angeles that more precipitation & cooler weather can come through. Around San Jose in the US, the climate type Csbk transitions to the climate type Csbl in San Jose and the climate type Cslk in San Francisco; the cities of Gilroy & Los Gatos have mountains to the south. From the valleys north of the San Francisco Bay in the US, the climate type Csbk transitions to the climate type Csak to the north within those valleys; those valleys are surrounded by mountains to the east & west in each case and by the San Francisco Bay to the south. From the cities between Coimbra & Porto in Portugal, the climate type Csbk transitions to the climate type Csak to the south and the climate type Cfbk to the north.
I could not find the climate type Csbk in Africa or Australia because those continents' points in the southern hemisphere farthest from the equator are too close to the equator for the winter to yield a fourth letter of 'k' or lower, and there are no significant highlands near the west coast to force such cool winters (unlike, for instance, Johannesburg in South Africa having a higher elevation and therefore having the climate type Cfbk near lowlands with the climate type Cfbl).
Csll/Cslk
The climate types Csll/Cslk are rare. I could only find them in Chile as well as in California & Oregon in the US. In Chile, the transition between the climate types Csll & Cslk is continuous going toward the pole on the west coast from Viña del Mar to Lebu along the Pacific Ocean in the latitude range of 33.00-37.61 degrees. There, the climate types Csll/Cslk transition to climate types with the first letter B (arid or semi-arid) to the north (toward the equator), the climate type Cflk toward Temuco to the southeast, and the climate type Csbk across the Coast Range to the east. In California in the US, the climate type Csll exists between the cities of Monterey & Salinas in the latitude range of 36.60-36.68 degrees and around Richmond at a latitude of 37.95 degrees; from Monterey & Salinas, the climate type Csll transitions to the climate type Csak toward Gonzalez to the southeast and to the climate type Csbk around the Monterey Bay toward Santa Cruz to the north, while mountains or the Pacific Ocean lie in other directions, and from Richmond, the climate type Csll transitions to the climate type Csbk toward other cities around the San Pablo Bay and to the climate type Csbl toward Oakland to the south, while mountains lie in other directions. The climate type Cslk also exists in California & Oregon in the US in disconnected parts of the northern part of the west coast along the Pacific Ocean, specifically between San Francisco & Point Arena in the latitude range of 37.78-38.92 degrees, between Shelter Cove & Eureka in the latitude range of 40.03-40.80 degrees, and between Klamath (in California in the US) & North Bend (in Oregon in the US) in the latitude range of 41.53-43.41 degrees (though in the last of those latitude ranges, the city of Denmark in Oregon in the US at a latitude of 42.89 degrees has the climate type Cflk, as it happens to get a little too much rain in the third-driest month of the summer to qualify with the climate type Cslk, and the city of Coos Bay in Oregon in the US at a latitude of 43.38 degrees has the climate type Dflk, as it happens to get a little too much rain in the third-driest month of the summer and has too few months with mean temperatures of at least 10 degrees Celsius to qualify with the climate type Cslk); between those sections, the climate type Cslk transitions to the climate type Dslk, and the climate type Cslk transitions to the climate type Csbk to the south (toward Palo Alto in the San Francisco Bay area) & the climate type Dflk to the north along the west coast of Oregon on the Pacific Ocean, while mountains lie to the east. The amount of precipitation decreases closer to the equator. Additionally, the fact that these climates exist at lower latitudes in South America than in North America adds credence to the idea that the Pacific Ocean is cooler in the southern hemisphere than in the northern hemisphere, which in turn is cooler than the Atlantic Ocean in the northern hemisphere.
The climate types Csll/Cslk do not exist in Europe, South Africa, or Australia. South Africa & Australia are too close to the equator for summers to be so mild & dry. Europe is too affected by the Gulf Stream in the Atlantic Ocean, so at latitudes close enough to the poles where the climate types Csll/Cslk arise in North America & South America, either the summer temperature is too high (with the third letter being 'b' or higher) or the summer is too wet for the second letter to be 's' (and in the second case, there may also be too few months of the year with mean temperatures of at least 10 degrees Celsius for the first letter to be C (subtropical) instead of D (intermediate)).
Dfak
Before I get into the climate type Dfak, I will make a broader statement about climate types with the first letter D (intermediate). I could not find any such climate types in Africa or Oceania (with the exception to the latter of Christchurch in New Zealand), as those continents are too close to the equator for there to be fewer than 8 months with mean temperatures of at least 10 degrees Celsius. I won't repeat this for the following discussions of every climate type with the first letter D (intermediate) that I could find.
I could find the climate type Dfak around Xi'An in China at a latitude of 34.26 degrees, around Lianyungang in China at a latitude of 34.60 degrees, around Qingdao in China at a latitude of 36.07 degrees, in a large swath of North America in the latitude range of 35.20-41.07 degrees (mostly in the northern parts of the lower southeastern part of the US, most of the upper southeastern part of the US, most of the southern Mid-Atlantic part of the US close to the east coast along the Atlantic Ocean, the parts of the northern Mid-Atlantic part of the US very close to the east coast along the Atlantic Ocean, and the southern parts of the Midwest of the US, with the cities of Montauk in New York, Richmond in Virginia, Wichita in Kansas, and Amarillo in Texas forming a parallelogram that roughly covers the area in question), around Gangneung in South Korea at a latitude of 37.75 degrees, around Sendai in Japan at a latitude of 38.27 degrees, around Ankara in Turkey at a latitude of 39.93 degrees, around Tbilisi in Georgia at a latitude of 41.72 degrees, cities in Europe to the east (more inland) & northwest (on the coast as well as inland) of the Adriatic Sea in the latitude range of 42.00-45.47 degrees), in Europe around the cities at the central latitudes of the Black Sea in the latitude range of 44.17-45.03 degrees, between the cities of Valence & Lyon in France in the latitude of 44.93-45.76 degrees, around Budapest in Hungary at a latitude of 47.49 degrees, and around Bratislava in Slovakia at a latitude of 48.14 degrees. Additionally, I could find the climate type Dfak in other isolated parts of North America, specifically in the US around Dayville in Oregon at a latitude of 44.47 degrees and around Lewiston in Idaho at a latitude of 46.41 degrees; both of those places have climate types that almost fall below the precipitation threshold for climate types with the first letter B (arid or semi-arid), and both of those places are in narrow valleys at low or moderate elevations above sea level far from the ocean, so there is less continuity in climate types going outside of those areas. Thus, the latitudes where the climate type Dfak occurs suggest that the in the northern hemisphere, the Black Sea & Adriatic Sea (partly aided by the Gulf Stream in the Atlantic Ocean) in Europe are warmer than the western part of the Atlantic Ocean near North America, which in turn is warmer than the western part of the Pacific Ocean near Asia, though the presence of the climate type Dfak in China at lower latitudes than in North America may have more to do with China being blocked by the Korean Peninsula & the islands of Japan from getting warm moist air over the western part of the Pacific Ocean.
From Xi'An in China, which is at a slight elevation above sea level, the climate type Dfak transitions to climate types with the first letter B (arid or semi-arid) to the west, north, and northeast, and to the climate type Cfak to the south & east. From Lianyungang in China, the climate type Dfak transitions to the climate type Cfak to the south along the coast of the Yellow Sea toward Yancheng and the climate type Dfao to the north along the coast of the Yellow Sea toward Rizhao as well as to the west (inland). From Qingdao in China, the climate type Dfak transitions to the climate type Dfao to the southwest along the coast of the Yellow Sea toward Rizhao, to the northeast into the Shandong Peninsula toward Yantai along the coast of the Yellow Sea, and to the northwest & west (inland) toward Weifang & Taian. From the places with the climate type Dfak in North America, the climate type Dfak generally transitions to the climate type Cfak to the south, the climate type Dfao to the north along the east coast next to the Atlantic Ocean as well as to the west inland, and to climate types with the first letter B (arid or semi-arid) further to the west (much more inland). Gangneung in South Korea is surrounded by mountains. From Sendai in Japan, the climate type Dfak transitions to the climate type Cfak to the south & west toward Tokyo & Niigata and the climate type Dfao to the north toward Sapporo, although Sendai is also mostly surrounded by mountains and Sapporo is on a different (though nearby) island. Ankara in Turkey meets all of the criteria for the climate type Dsak except for the requirement that the single wettest month be in the winter half of the year, so it having the climate type Dfak is a quirk of my modification to the Trewartha categorization (much like İstanbul in Turkey having the climate type Cfak). From Tbilisi in Georgia, the climate type Dfak transitions to climate types with the first letter B (arid or semi-arid) to the southeast; it is otherwise surrounded by mountains. From the cities near the Adriatic Sea in Europe, the climate type Dfak transitions from the cities west or northwest of the Adriatic Sea to the climate type Cfak to the south, while mountains lie further to the west, and the climate type Dfak transitions from the cities east of the Adriatic Sea but a bit inland (which arguably includes the cities of Bratislava in Slovakia & Budapest in Hungary, as they, like Novi Sad & Belgrade in Serbia, are in the Carpathian Basin) to the climate type Cfak to the west (along the coast of the eastern part of the Adriatic Sea) and the climate types Dfbk, Dfao, or Dfbo in more inland or elevated parts of the Carpathian Basin. From the cities between Valence & Lyon in France, the climate type Dfak transitions to the climate type Cfak to the south and to the climate type Dfbk in other directions. From the cities around the central latitudes of the Black Sea in Europe, the climate type Dfak transitions to the climate type Dfao along the coast of the northern part of the Black Sea as well as more inland in those directions & the climate type Cfak along the coast of the southern part of the Black Sea.
It is worth explaining further how even though all of these places have the climate type Dfak, the climates still have important differences, particularly with respect to average amounts of precipitation per year and the distribution of precipitation through the year. In North America, almost all places with the climate type Dfak get a lot of warm moist air through the year from the Gulf of Mexico and from the Gulf Stream in the Atlantic Ocean even if they are relatively far inland, as that part of the continent has no major mountain ranges to the south that lie east to west as to block the flow of air from the equator or from the pole, so these places get an average of over 1,000 millimeters of precipitation per year, and the distribution is almost always either uniform or with slightly drier winters; only Montauk in New York in the US gets an average of over 1,000 millimeters of precipitation per year but has a slightly drier summer, though the skew in the distribution is marginal. The only exceptions in the US are Wichita, Dodge City, and Amarillo, which are farther inland, away from those tracks of warm moist air from the Gulf of Mexico, and closer to the rain shadow of the Rocky Mountains, so they have much drier winters as most of their precipitation comes when the land heats up enough in the summer half of the year to more strongly draw in warm moist air from the Gulf of Mexico, and they respectively get averages of less than 900, 600, and 500 millimeters of precipitation per year. By contrast, in Asia, particularly in East Asia, places that have the climate type Dfak almost always have much drier winters due to the proximity of the high-pressure area over Lake Baikal in Russia in the winter half of the year, but the amount of precipitation is more sensitive to location, as Gangneung in South Korea & Sendai in Japan are much more consistently surrounded by the Pacific Ocean & its warm moist air, so they get averages of over 1,200 millimeters of precipitation per year, whereas Xi'An, Qingdao, and Lianyungang in China are more inland or are blocked from getting warm moist air by the mountains of the islands of Japan & the Korean Peninsula, so they get averages of less than 900 millimeters of precipitation per year (possibly much less, depending on the specific location). Tbilisi in Georgia gets less than 500 millimeters of rain per year as it is far inland, not close to any inland seas, and mostly surrounded by mountains, and its winters are slightly drier. The cities in Europe on the western side of the Adriatic Sea, whether on the [east] coast or more inland, as well as those inland to the east of the Adriatic Sea & in the Carpathian Basin generally get averages of less than 800 millimeters of precipitation per year because of the rain shadow effects of the Apennine Mountains in Italy & other mountains in the Balkan Peninsula; those mountains may also break up the subtropical ridge that would otherwise cause a drier summer, so the distribution of precipitation is uniform or leads to slightly drier winters. The exceptions are Turin & Milan in Italy, which seem to get more precipitation despite being more inland (which I struggle to explain, though they may be affected by low-pressure systems that form over Genoa & lead to Genoa getting so much rain through the year, despite a drying trend in the summer & a moistening trend in the winter, to have the climate type Cfak instead of the climate type Csak west & south of the Apennine Mountains in Italy), as well as Rijeka in Croatia, which is on the [west] coast of the eastern side of the Adriatic Sea, so a smaller or less persistent subtropical ridge may form there in the summer to produce slightly drier summers and much higher precipitation levels of more than 1,500 millimeters on average. The cities in France between Valence & Lyon are more inland, away from both the west coast along the Atlantic Ocean (though still along the path of mild moist air following the Gulf Stream) & the south coast along the Mediterranean Sea, so they get averages of around 850 millimeters of precipitation per year, uniformly distributed through the year. The cities in Europe in the middle latitudes of the Black Sea on the coasts on either side get averages of less than 800 millimeters of precipitation per year due to rain shadows to the west blocking the moist prevailing westerlies, but moisture picks up more over the Black Sea, which is why cities to the west of the Black Sea (on the east coast) are drier than cities to the east of the Black Sea (on the west coast) at the same latitude, though apparently the Black Sea is too close to the pole and too far removed from the Gulf Stream of the Atlantic Ocean & its effects on the Mediterranean Sea as well as the western part of Europe for a subtropical ridge to form & lead to drier summers east of the Black Sea.
The climate type Dfak does not occur in South America. It cannot occur in Chile because Chile lies to the west of the Andes Mountains, so the climate of Chile would be subject to the subtropical ridge closer to the equator and the prevailing westerlies bringing mild moist air closer to the pole, meaning that the first three letters of the climate type Dfak cannot occur together in those places. It does not occur in Argentina even closer to the pole relative to the places that have the climate types Cfak or Cfbk because the rain shadow effect to the east of the Andes Mountains combined with the cooler mixing waters of the Atlantic Ocean & Antarctic Ocean at those latitudes along the east coast of Argentina means that those places have climate types with the first letter B (arid or semi-arid). This is also why the climate types Dfao/Dfac, Dfbk, Dfbo/Dfbc, and Dflo/Dflc do not occur in South America (though, as will become clear in later sections, the climate type Dflk does occur in South America), so I will not mention those again.
Dfbk
The climate type Dfbk occurs almost exclusively in Europe and covers a large area & latitude range there, as the latitude range is 43.86-57.71 degrees. In Europe, it occurs in sections of the line of cities between Sarajevo in Bosnia & Herzegovina and Graz in Austria in the latitude range of 43.86-47.07 degrees, around most of the northern half of France in the latitude range of 45.78-51.04 degrees with the cities of Nantes, Clermont-Ferrand, and Dijon forming the southern edge of that area, the line of cities between Southampton & Colchester in the UK in the latitude range of 50.90-51.89 degrees, sections of the line of cities of Switzerland north of the Alps Mountains in the latitude range of 46.20-47.37 degrees as well as parts of Switzerland directly south of the Alps Mountains (though these tend to be less populated), most of Luxembourg, Belgium, the Netherlands, and Germany, around Prague in the Czech Republic at a latitude of 50.09 degrees, around Wrocław & Szczecin in Poland (which are close to the border with Germany) at latitudes of 51.11 & 53.43 degrees, and the island of Zealand in Denmark along with cities in Sweden across the Oresund from Denmark. Outside of Europe, the climate type Dfbk is rare. In Oceania, it occurs around Christchurch in New Zealand at a latitude of 43.53 degrees; this is the only climate type with the first letter D (intermediate) that occurs in Oceania. In North America, it occurs unusually around Nantucket in the US on an island in the western part of the Atlantic Ocean (i.e. just off of the east coast of the US) at a latitude of 41.28 degrees. It also occurs around the cities of Abbotsford & Vancouver in Canada on its west coast along the Pacific Ocean in the latitude range of 49.05-49.26 degrees.
From the areas of France that have the climate type Dfbk, the climate type Dfbk transitions to the climate type Cfbk in the western part and the climate type Dfak in the eastern part. From the areas of the UK that have the climate type Dfbk, the climate type Dfbk transitions to the climate type Dflk to the northwest & southeast. Most of the rest of Europe that has the climate type Dfbk is bounded to the north by the North Sea, the south by the Alps Mountains, and the west by the Atlantic Ocean (including France in this area), so the climate type Dfbk generally transitions to the climate type Dfbo to the east, though in the Netherlands & Denmark, the climate type Dfbk transitions to the climate type Dflk toward more oceanic areas, and from Vienna, the climate type Dfbk transitions to the climate type Dfak to the east. From Nantucket in the US, the climate type Dfbk transitions to the climate type Dfak hopping to the west to the island of Martha's Vineyard and the climate type Dfbo hopping to the north to the mainland. From Vancouver in Canada, the climate type Dfbk transitions to the climate type Dflk to the south and the climate type Dsbk hopping to the west to the city of Nanaimo on Vancouver Island, while mountains lie to the north & east. From Christchurch in New Zealand, the climate type Dfbk transitions to the climate type Cfbk to the north.
It is worth explaining further how even though all of these places have the climate type Dfbk, the climates still have important differences, particularly with respect to average amounts of precipitation per year. In Europe, because various mountain ranges lie roughly along lines of latitude, thereby sharpening transitions between different climate types going between the equator & the pole, the climate type Dfbk is too far removed from climate types with the first letter C (subtropical) & second letter 's' to consistently have drier summers. However, one trend that is clear is that because these locations are closer to the pole, despite the effect of the Gulf Stream in the Atlantic Ocean, they get averages of less than 1,000 millimeters of precipitation per year, and that level decreases closer to the pole or farther inland; the only exception to having an average of less than 1,000 millimeters of precipitation per year that I could find is Brest in France due to its coastal location along the Atlantic Ocean in the northwestern corner of France. By contrast, in North America, although Vancouver & Abbotsford in Canada are in a rain shadow of mountains to the west (on Vancouver Island), they get more than 1,000 millimeters of rain per year by being on the windward side of even taller mountains to the east, and the rain shadow effect is strong enough to make the summers much drier (such that the climate type almost qualifies as Dsbk instead of Dfbk). Additionally, Nantucket in the US has the climate type Dfbk because of the mixing of the warm moist air & water associated with the Gulf Stream in the Atlantic Ocean with its colder backflow from the pole despite being east of the mainland US, and the warmth of the Gulf Stream in the Atlantic Ocean ensures average precipitation levels of more than 1,000 millimeters per year. Meanwhile, in Oceania, Christchurch in New Zealand (which is at a similar latitude as Nantucket in the US and at a lower latitude than most of Europe as well as Vancouver & Abbotsford in Canada) has the climate type Dfbk because of the mixing of the warm moist air & water associated with the Pacific Ocean with the cooler air & water associated with the Antarctic Ocean despite being east of Australia, but it gets an average of less than 600 millimeters of precipitation per year because that air & those waters are colder than the corresponding air & water hitting Nantucket.
It is worth emphasizing that the climate type Dfbk only transitions to the climate type Dfak in three small areas and only two of these transitions are continuous over land (both of which are in Europe). One is in France, where the existence of the climate type Dfak is a continuation of the existence of the climate type Cfak closer to the equator, which itself is a quirk of the air over the Gulf Stream in the Atlantic Ocean mitigating the effects of the climate type Csak occurring on the south coast of France along the Mediterranean Sea. Another is going from Vienna in Austria toward Bratislava in Slovakia & other cities in the Carpathian Basin, as the lowlands of the Carpathian Basin & the slight rain shadow effects of surrounding mountains lead to higher temperatures in the summer but do not cut off moisture from over the Gulf Stream in the Atlantic Ocean or over the Adriatic Sea to an extent that would lead to climate types with the first letter B (arid or semi-arid). The third place is hopping over water in the US from Nantucket westward to Martha's Vineyard (as both are islands to the east of the mainland US). Otherwise, unlike the climate types Cfak & Cfbk which continuously transition between each other in broader areas of South America, Europe, Asia, and Australia, the climate types Dfak & Dfbk are disconnected on most continents because the conditions for each of those climate types to occur are different enough that those climate types must occur far from each other: given that these locations are close enough to the pole for the climate type D (intermediate) to arise with fewer than 8 months having mean temperatures of at least 10 degrees Celsius, having the third letter 'a' implies a more continental influence combined with warmer moist air from oceans that can usually only be found near an east coast, whereas having the third letter 'b' & fourth letter 'k' implies a more oceanic influence by itself or in the path of cooler moist air carried by the prevailing westerlies toward the west coast of a continent. This is why the third & fourth letters are so important, especially as Vancouver & Abbotsford in Canada with the climate type Dfbk have noticeably drier summers making them more prone to wildfires, whereas this is not the case for most places in North America with the climate type Dfak; these distinctions are not captured by the Trewartha categorization which would give all of these places the climate label Do with the third & fourth letters being optional.
Dflk
The climate type Dflk occurs in South America, especially in Chile, between the cities of Valdivia & Quellón in the latitude range of 39.81-43.10 degrees, around the city of Melinka (hopping from Quellón over water to an island closer to the pole) at a latitude of 43.90 degrees, and directly to the east of the Andes Mountains closer to the pole around the cities of Coyhaique & Cochrane at latitudes of 45.57 & 47.25 degrees (but although there are continuous connections by land in between without being broken up by mountains, the climate types differ a lot in between). The climate type Dflk occurs in North America directly on the west coast of the US (as the climate changes significantly even a bit more inland) between the cities of Coos Bay in Oregon & Neah Bay in Washington in the latitude range of 43.38-48.37 degrees, in the US around Bellingham in Washington at a latitude of 48.75 degrees, and along the west & north coasts of Victoria Island & Graham Island in British Columbia in Canada as well as around Ketchikan & Sitka on the west coast of the panhandle of Alaska in the US in the latitude range of 48.94-57.05 degrees. The climate type Dflk occurs in Europe in most of the British Isles (except for those areas already specified to have the climate type Dfbk), the north coast of Europe between Guernsey and Groningen, the Jutland Peninsula in Germany from Hamburg to the north, most of Denmark, and the south & west coasts of Norway between the cities of Kristiansand & Bergen, in the latitude range of 49.44-60.39 degrees. Thus, it is clear once again that the Pacific Ocean is colder in the southern hemisphere due to mixing with the Antarctic Ocean than in the northern hemisphere, which in turn is colder than the Atlantic Ocean, as the climate type Dflk occurs closer to the equator in South America, then North America, and finally Europe.
From the cities between Valdivia & Quellón in Chile, the climate type Dflk transitions to the climate type Cflk to the north, while the Andes Mountains lie to the east & the Reloncavi Sound lies to the south. Between the cities of Coyhaique & Cochrane in Chile, the climate type Dflk transitions to the climate type Dslk; from these areas, the climate type Dflk transitions to climate types with the first letter B (arid or semi-arid) to the east, while the Andes Mountains lie to the west. From the cities in North America where the climate type Dflk occurs, the climate type Dflk transitions to the climate type Cslk to the south, while mountains lie to the east in most sections of this region. Specifically along the west coast of Washington in the US, the climate type Dflk transitions to the climate type Dslk to the east where there are some but fewer & shorter mountains. Also, specifically around Bellingham in Washington in the US, the climate type Dflk transitions to the climate type Dfbk to the north (which is toward the pole, so I'm not sure how that transition occurs) and south, while mountains lie to the east. The cities in British Columbia in Canada & Alaska in the US which exhibit the climate type Dflk are all on or near the west coasts of islands that are otherwise mostly mountainous. In Europe, the climate type Dflk transitions on the British Isles to the climate type Dfbk in a southwest-to-northeast band around the city of London in the UK as discussed previously, while on the main continent, the climate type Dflk transitions from the north coast between the cities of Rouen in France & Groningen in the Netherlands to the climate type Dfbk to the south & east, from the Jutland Peninsula (encompassing parts of Denmark & Germany) to the climate type Dfbk to the south, and from Norway to the climate type Dflo along the coast in each direction (as the interior of Norway is almost entirely mountainous).
It is worth emphasizing that the climate type Dflk, where it occurs, often transitions to the climate type Dfbk. This is because both of those climate types, which feature relatively small differences between the hottest & coldest mean monthly temperatures, occur at middle latitudes along west coasts where prevailing westerlies consistently bring mild moist air year-round. This is unlike the dichotomy between the climate types Dfbk & Dfak. By contrast, this same reason explains why it is rare for the climate type Dflk to transition to the climate type Dflo; I could only see it in Norway over larger distances around its coast in either direction. Additionally, the presence of the climate type Dflk along west coasts, in some cases not too far from subtropical ridges that arise in the summer, explains why most places with the climate type Dflk do exhibit a drying trend in the summer, though not enough to suggest a vulnerability to wildfires; locations with the climate type Dflk in North America & South America are almost exclusively just on the west coasts of each continent along the Pacific Ocean and also happen to be on the windward sides of mountains relative to the prevailing westerlies, so these locations consistently get averages of more than 1,400 millimeters of precipitation per year distributed disproportionately in the winter half of the year, whereas in Europe, locations with the climate type Dflk are typically found more inland too, and there aren't as many significant mountain ranges that would lead to more precipitation on the windward side of the prevailing westerlies, so these locations (with few exceptions in places where there are mountains or hills, such as Glasgow in the UK and some of the cities along the south & west coasts of Norway, as those are more like places in North America & South America in precipitation levels & distributions) consistently get 700-900 millimeters of precipitation with only a slightly (if at all) drier summer.
Eflk
It may seem odd to discuss a climate type with the first letter E (subpolar) before finishing discussion of climate types with the first letter D (intermediate). The reason is that the climate type Eflk is rare, mostly occurring in small islands farther from land around latitudes of 60 degrees. I could find it around Adak in Alaska in the US in North America, Punta Arenas in Chile as well as the northern part of the island of Tierra del Fuego (divided between Chile & Argentina) in South America, and in Europe along the south coast of Iceland, in the Faroe Islands in Denmark, and around the islands of Røst & Værøy in Norway. The only exception to the island occurrence is Punta Arenas in Chile, from which the climate type Eflk transitions to the climate type Dflk to the northwest and to climate types with the first letter F (polar) or B (arid or semi-arid) in other directions; this is because of the cool moderation of the Antarctic Ocean. (The existence of the transition to the climate type Dflk going away from Punta Arenas in Chile on the mainland of South America is the reason I have discussed the climate type Eflk immediately after discussing the climate type Dflk; notably, the climate type Eflk does not continuously transition anywhere to the climate type Eflo.) Otherwise, the islands in the northern hemisphere where the climate type Eflk occurs generally lie to the west of the nearest major continent or equidistant between North America & Eurasia. This also means that Punta Arenas in Chile as well as the northern part of the island of Tierra del Fuego (divided between Chile & Argentina), which are not to the west of their major continent, get averages of less than 400 millimeters of precipitation per year distributed roughly uniformly over the year, whereas the other locations, which are islands to the west of their respective major continents, get averages of at least 800 millimeters of precipitation per year (in some cases more than 1,300 millimeters) with much drier summers.
Dsak/Dsbk/Dslk
Although the discussion is returning to climate types with the first letter D (intermediate), it is covering those with the second letter 's' (dry summers) before returning to those with the second letter 'f' (humid summers) because these climates are found almost exclusively in North America, specifically in the US (so all places below will be from the US unless otherwise specified). In particular, places with the climate types Dsak/Dsbk/Dslk tend to be at higher latitude near a west coast but in a rain shadow for the summer to be sufficiently dry or at a lower latitude near a west coast but on the windward side of a mountain to be sufficiently cool (that the climate type wouldn't have the first letter C (subtropical)), either way reinforcing the dry summers from the subtropical ridge. I could find the climate type Dsak around isolated cities in the states of California, Oregon, Washington, and Idaho that are in valleys closer to the west coast or are on the windward (western or southern relative to the prevailing westerlies in the northern hemisphere) side of the major mountains, including Groveland in California at a latitude of 37.83 degrees, Placerville in California at a latitude of 38.73 degrees, Clearlake in California at a latitude of 38.96 degrees, Grass Valley in California at a latitude of 39.22 degrees, cities in the valley between Yreka in California (not to be confused with Eureka in California, at a similar latitude but on the west coast leading to the climate type Cslk) & Grants Pass in Oregon in the latitude range of 41.73-42.44 degrees (with the exception of Ashland in Oregon in the middle of that valley due to its higher elevation above sea level, leading to the climate type Dsbk), The Dalles in Oregon at a latitude of 45.60 degrees, Arlington in Oregon at a latitude of 45.72 degrees, cities between Pendleton in Oregon & Walla Walla in Washington in the latitude range of 45.67-46.07 degrees, and Ahsahka in Idaho at a latitude of 46.50 degrees. Finally, I could find the climate type Dsak around Boise in Idaho in the US at a latitude of 43.62 degrees, though this seems slightly anomalous (though the drying trend in the summer is clear), as the climate type Dsak there is surrounded by climate types with the first letter B (arid or semi-arid).Groveland, Placerville, and Grass Valley in California lie on the eastern edge of the Central Valley along the western slopes of the Sierra Nevada, so from these locations, the climate type Dsak transitions to the climate type Csak to the west. From the area between the cities of Yreka in California & Grants Pass in Oregon, apart from the transition to the climate type Dsbk in between around the city of Ashland in Oregon, the climate type Dsak transitions to the climate type Dsbk to the south and the climate type Dsbo to the east. From around The Dalles in Oregon, the climate type Dsak transitions to the climate type Dsbo to the north, east, and south, and the climate type Dsbk to the west. From around Arlington in Oregon, the climate type Dsak transitions to the climate type Dsbo to the west and to climate types with the first letter B (arid or semi-arid) in other directions. From the area around cities between Pendleton in Oregon & Walla Walla in Washington, the climate type Dsak transitions to climate types with the first letter B (arid or semi-arid) to the west & north and the climate type Dsbk to the northeast, while mountains lie to the east & south. Finally, from around Ahsahka in Idaho, the climate type Dsak transitions to the climate type Dfbo to the south and the climate type Dfak to the west, while mountains lie to the north & east; this is because Ahsahka in Idaho lies on the northern edge of a basin surrounded by mountains, which is the windward side relative to the prevailing westerlies bringing mild moist air in the winter, whereas places on the leeward side of mountains on the other side of that basin have very different distributions of precipitation over the year.
I could find the climate type Dsbk more continuously in the valleys of the western parts of the states of Oregon & Washington, close to the west coast but blocked by mountains, specifically between the cities of Canyonville in Oregon & Seattle in Washington in the latitude range of 42.93-47.61 degrees, although there are portions in the middle that transition to other climate types like Dfbk. I could find the climate type Dsbk in the state of California around the city of Willits at a latitude of 39.41 degrees, around the city of Susanville at a latitude of 40.42 degrees, and between the cities of Mount Shasta (separate from the actual mountain called Mount Shasta, which is just to the northwest of the city) & Weed in the latitude range of 41.31-41.42 degrees. I could find the climate type Dsbk around the city of Hood River in Oregon at a latitude of 45.71 degrees. Finally, I could find the climate type Dsbk between the cities of Dayton & Pomeroy in Washington in the latitude range of 46.32-46.47 degrees.
From the continuous area between the cities of Canyonville in Oregon & Seattle in Washington, apart from the aforementioned transition to the climate type Dfbk in between, the climate type Dsbk transitions to the climate types Dfbk/Dflk to the north, and that region, like the area around the city of Willits in California, is otherwise surrounded by mountains. From around the city of Susanville in California, the climate type Dsbk transitions to the climate type Dsbo to the west, north, and east, while mountains lie to the south. From the area between the cities of Mount Shasta & Weed in California, the climate type Dsbk transitions to the climate type Dsak to the north and the climate type Dsbo to the east, while mountains lie to the south & west. From around the city of Hood River in Oregon, the climate type Dsbk transitions to the climate type Dsak to the east, while mountains lie in other directions. From the area between the cities of Dayton & Pomeroy in Washington, the climate type Dsbk transitions to the climate type Dfak to the east, the climate type Dsbo to the northeast, climate types with the first letter B (arid or semi-arid) to the north, northwest, and west, and the climate type Dsak to the southwest, while mountains lie to the south & southeast.
I could find the climate type Dslk in isolated places in the US & Canada, including around the city of Fort Bragg in California at a latitude of 39.45 degrees, around the city of Mineral in California at a latitude of 40.36 degrees, around the city of Olympia in Washington at a latitude of 47.04 degrees, around the city of Port Angeles in Washington at a latitude of 48.11 degrees, and around the city of Victoria on Vancouver Island in British Columbia at a latitude of 48.43 degrees. I could also find the climate type Dslk in Chile in isolation around the cities of Balmaceda & Chile Chico at the latitudes of 45.91 degrees & 46.54 degrees, which are the only places in South America (or on any continent outside of North America) to have climate types with the first letter D (intermediate) and the second letter 's' (dry summer) as the Andes Mountains to the west are at the right height to allow the prevailing westerlies to bring mild moist air in the winter half of the year but reinforce the subtropical ridge ensuring a dry summer half of the year; from these places, the climate type Dslk transitions to climate types with the first letter B (arid or semi-arid) to the east and to the climate type Dflk to the north & south. From Fort Bragg in California in the US, the climate type Dslk transitions to the climate type Cslk in both directions (north & south) along the west coast, while mountains lie to the east. Mineral in California in the US is surrounded by mountains in all directions. From Olympia in Washington in the US, the climate type Dslk transitions to the climate type Dsbk to the south, east, and northeast, while mountains lie to the west. From Port Angeles in Washington in the US, the climate type Dslk transitions to the climate type Dflk along the north coast to the west and to the climate type Dsbk following the same coast to the south after having followed it to the east, while mountains lie to the south. Thus, it is rare for the climate type Dslk to transition to the climate type Dsbk, and the climate type Dsbk doesn't seem to transition anywhere to the climate type Dsak due to the specific conditions near mountains required for the climate type Dsak to exist.
The climate types Dsak/Dsbk/Dslk do not exist in Europe because the relative warmth of the Gulf Stream in the Atlantic Ocean combined with a lack of mountains parallel to lines of longitude ensure that closer to the equator, the climate is warm enough with a dry summer for the first letter to be C (subtropical) if the second letter is 's', while closer to the pole, the cooling of the climate to the first letter D (intermediate) forces the second letter to change to 'f' as the subtropical ridge causing a drying trend in the summer can no longer be supported in such an oceanic environment.
Dsao/Dsbo/Dslo
I could find the climate type Dsao around the city of Yerevan in Armenia at a latitude of 40.18 degrees. The existence of the climate type Dsao around Yerevan in Armenia is just because of its anomalous climate. In particular, that area has a moderate to high elevation above sea level, gets an average of less than 400 millimeters of precipitation per year, and is surrounded by areas with climate types with the first letter B (arid or semi-arid); furthermore, because precipitation is concentrated around both equinoxes rather than one of the solstices (which is unusual), that area would also have a climate type with the first letter B (arid or semi-arid) with marginally less precipitation per year. Additionally, it is close to the center of Eurasia, very far from the Atlantic & Pacific Oceans; although the nearest major bodies of water are the Black & Caspian Seas around 200 miles away as the crow flies in each direction, these are not big enough bodies of water to moderate the climate to something more predictable, evinced by the fact that the city of Kars in Turkey, which is less than 100 miles to the west as the crow files and should therefore naively have a stronger trend of dry summers, has a climate type with the second letter 'f' instead of 's'.
Otherwise, climate types with the first letter D (intermediate), second letter 's' (dry summers), and third letter 'o' are exclusive to North America, especially in the states of California, Oregon, and Washington in the US. These states all have a west coast along the Pacific Ocean, but these climate types occur farther inland, specifically in the rain shadow of mountains to the west but not far enough inland for the effect of the prevailing westerlies to become completely nullified. This combination, along with slight to moderate elevation above sea level in many cases, ensures the combination of fewer than 8 months with average temperatures of at least 10 degrees Celsius, dry summers, and the coldest month having an average temperature below 0 degrees Celsius. These conditions do not exist in Europe as there are no significant mountain ranges parallel to lines of longitude, South America as the mountains near the coast are too short to support a drying trend in the summer (and there isn't enough landmass far enough from the west coast along the Pacific Ocean except on the leeward side of the Andes Mountains, which are tall enough that the prevailing westerlies don't really affect areas on that leeward side), or Africa or Australia which are too close to the equator.
I could find the climate type Dsao in Washington in the US, around the city of Yakima at a latitude of 46.60 degrees and between the cities of Wenatchee & Tonasket along the Okanagon & Columbia Rivers in the latitude range of 47.42-48.71 degrees. These places are all at marginal to slight elevations above sea level, are all less than 200 miles away as the crow flies from the west coast along the Pacific Ocean, and are all bounded by mountains at least to the west (and also to the east for the cities between Omak & Tonasket), so the combination of the prevailing westerlies bringing mild moist air in the winter and the mountains to the west creating a rain shadow that supports the subtropical ridge in the summer ensures more consistently dry summers & wet winters with average precipitation levels of around 300 millimeters or less per year; the low elevations also explain why the hottest month has an average temperature high enough to have the third letter 'a' instead of 'b' or lower. From Yakima in Washington in the US, the climate type Dsao transitions to the climate type Dsbo to the north and to climate types with the first letter B (arid or semi-arid) to the east. From the cities between Wenatchee & Bridgeport in Washington in the US, the climate type Dsao transitions to the climate type Dsbo to the east and to climate types with the first letter B (arid or semi-arid) to the south & southeast. From the cities between Bridgeport & Tonasket in Washington in the US, the climate type Dsao transitions to the climate type Dfao to the north within the valley (as those areas are close enough to the pole & blocked from the prevailing westerlies over the Pacific Ocean by enough mountains that the dry summer trend no longer holds, so instead the warm summer draws in more moisture), while mountains lie to the east.
I could find the climate types Dsbo/Dslo in the US, specifically in the eastern parts of the states of Washington & Oregon and in the northeastern part of the state of California. In particular, I could find the climate type Dsbo in the quadrilateral area whose corners are given by the cities of Herlong in California, McArthur in California, Klamath Falls in Oregon, and Summer Lake in Oregon in the latitude range of 40.14-42.97 degrees, around the city of Burns in Oregon at a latitude of 43.59 degrees, between the cities of Prineville & Madras in Oregon in the latitude range of 44.30-44.63 degrees, between the cities of La Grande & Elgin in the valley of the Grande Ronde River in Oregon in the latitude range of 45.33-45.57 degrees, between the cities of Wasco in Oregon & Goldendale in Washington in the latitude range of 45.59-45.82 degrees, in the quadrilateral area whose corners are given by the cities of Pullman in Washington, Deer Park in Washington, Coeur d'Alene in Idaho, and Moscow in Idaho in the latitude range of 46.73-47.96 degrees, and between the cities of Ellensburg & Leavenworth in Washington in the latitude range of 47.00-47.60 degrees. I could only find the climate type Dslo in a triangular area whose corners are given by the cities of Chiloquin, Chemult, and Fort Rock in Oregon in the latitude range of 42.58-43.36 degrees. All of these places have slight to moderate elevations (moderate at lower latitudes & slight at higher latitudes) above sea level.
From the quadrilateral area whose corners are given by the cities of Herlong in California, McArthur in California, Klamath Falls in Oregon, and Summer Lake in Oregon, the climate type Dsbo transitions to the climate type Dsbk to the southwest, the climate type Dsak to the west, the climate type Dslo to the north, and climate types with the first letter B (arid or semi-arid) to the east. From around the city of Burns in Oregon, the climate type Dsbo transitions to climate types with the first letter B (arid or semi-arid) seemingly in every direction. From the area between the cities of Prineville & Madras in Oregon, the climate type Dsbo transitions to the climate type Dsbk to the southwest and to the climate type Dflo to the south, while mountains lie in other directions. From the area between the cities of La Grande & Elgin in the valley of the Grande Ronde River in Oregon, the climate type Dsbo transitions to the climate type Dfbo to the east and to climate types with the first letter B (arid or semi-arid) to the south, while mountains lie in other directions. From between the cities of Wasco in Oregon & Goldendale in Washington, the climate type Dsbo transitions to the climate type Dsak to the west & east and to climate types with the first letter B (arid or semi-arid) to the north & south. From the quadrilateral area whose corners are given by the cities of Pullman
in Washington, Deer Park in Washington, Coeur d'Alene in Idaho, and Moscow
in Idaho, the climate type Dsbo transitions to climate types with the first letter B (arid or semi-arid) to the west and to the climate type Dfak to the south, while mountains lie to the north & east. From the area between the cities of Ellensburg & Leavenworth in Washington, the climate type Dsbo transitions to the climate type Dsao to the south & east, while mountains lie to the north & west; farther to the west of Leavenworth is the Seattle metropolitan area with the climate type Dsbk, but this isn't truly a continuous transition as the terrain is broken up by mountains in between. From the triangular area whose corners are given by the cities of Chiloquin, Chemult, and Fort Rock in Oregon, the climate type Dslo transitions to the climate type Dsbo to the south & east and to the climate type Dsbk to the north, while mountains lie to the west (beyond which is an area with the climate type Dsak).
It is rare for the climate type Dsao to transition to the climate type Dsbo, and the only such transitions are arguably not continuous as they happen in mountainous areas. Additionally, it is notable that the climate type Dsao occurs in North America closer to the pole than the climate types Dsbo/Dslo. I'm not entirely sure why this is, though it may be because the places where the climate type Dsao occurs are at much lower elevations above sea level than the places where the climate types Dsbo/Dslo occur.
Dfao/Dfac/Dfbo/Dfbc/Dflo/Dflc/Eflo/Eflc/Efld
I have lumped together the climate types Dfao/Dfac/Dfbo/Dfbc/Dflo/Dflc/Eflo/Eflc/Efld for the following reasons. First, the climate types Eflo/Eflc/Efld, where they occur on major continents (as opposed to small islands), transition from climate types Dfbo/Dfbc/Dflo/Dflc, not from the climate type Eflk (which only occurs on islands west of major continents). Second, especially in North America but also to some extent in Eurasia, the transitions between the climate types Dfao/Dfbo/Dfbc/Dflo/Dflc, unlike the transitions from the climate type Cfak to the climate type Dfak and then to the climate Dfao, do not occur along essentially single boundaries in each continent. For example, in North America, it is sometimes possible in places like South Dakota & North Dakota in the US, for reasons that may be related to the urban heat island effect (in which an urban area tends to be hotter than its non-urban surroundings due to human-made buildings & surfaces absorbing more thermal energy) but which I otherwise find hard to explain on those scales, to follow a line of longitude toward the pole in which the climate type transitions from Dfbo to Dfao and then to Dfbo again. That said, because the climate types Dfao/Dfac/Dfbo/Dfbc (especially the climate types Dfao/Dfac) tend to occur closer to the east coasts of the major continents of North America & Eurasia because the tapering influence of the warm ocean currents along the east coast gives the combination of warm summers & cold winters, it is still generally the case that warmer climate types occur closer to the pole when closer to the ocean. Third, the lesser population closer to the pole in the northern hemisphere restricts the availability of climate data, which especially affects places with climate types with the first letter E (subpolar). Fourth, upon approaching the pole, the transition from the prevailing westerlies to the polar easterlies and the shrinking of distances along lines of latitude together mean that the climate types of the northern parts of North America & Eurasia have much rougher boundaries but can, from a coarse-grained perspective, be roughly described as starting with the first letter E (subpolar) or F (polar). Thus, the lack of smoothness & lesser predictability in the boundaries between these particular climate types means that I will use less precision when describing where these climate types arise and how one may transition to others.
I will first note where the climate types Dfao/Dfac/Dfbo/Dfbc/Dflo/Dflc/Eflo/Eflc/Efld occur in isolation, meaning that where one such climate type occurs, it transitions to very different climate types (not just a climate type that at most goes between the first letter E (subpolar) & the first letter D (intermediate) and changes at most either the third or fourth letter by a single unit) in surrounding areas. The climate type Dfao occurs more in isolation around Kabul in Afghanistan at a latitude of 34.53 degrees, in the US around Salt Lake City in Utah & Elko in Nevada at respective latitudes of 40.76 degrees & 40.83 degrees, around Bishkek in Kyrgyzstan at a latitude of 42.87 degrees, and around Almaty in Kazakhstan at a latitude of 43.28 degrees. These places are surrounded by climate types with the first letter B (arid or semi-arid) and are in highland areas far from any major body of water, so they are cold and themselves dry. The climate type Dfbo occurs more in isolation in the US around Flagstaff in Arizona at a latitude of 35.20 degrees and around Blacksburg in Virginia at a latitude of 37.23 degrees as they are also in highland areas far from any major body of water, though the position of Blacksburg in Virginia in the US in the path of warm moist air from the Gulf of Mexico implies much more precipitation; thus, from Flagstaff in Arizona in the US, the climate type Dfbo transitions to climate types with the first letter B (arid or semi-arid) in all directions, while from Blacksburg in Virginia in the US, the climate type Dfbo transitions to the climate type Dfak to the southwest, south, and east, while mountains lie in other directions. The climate type Dfbc occurs more in isolation around the cities of Karaganda & Astana in Kazakhstan at latitudes of 49.80 degrees & 51.15 degrees, transitioning to climate types with the first letter B (arid or semi-arid) in all directions (including between those cities). Arguably, the climate type Dfbc also occurs more in isolation around the city of Fairbanks in Alaska in the US at a latitude of 64.84 degrees, because although the transition of the climate type Dfbc to the climate type Eflc to the south & west (while mountains lie to the north & east) is slightly more continuous, that latitude is by far the closest to the pole compared to anywhere else that the climate type Dfbc occurs and is in fact the closest to the pole that I could find of any location with any climate type with the first letter D (intermediate); for comparison, the next-closest location to the pole with the climate type Dfbc is around the city of Yekaterinburg in Russia at a latitude of 56.84 degrees (and that is part of a more continuous area with the climate type Dfbc).
Otherwise, these climate types generally transition continuously from one to another. The climate type Dfao in North America & Asia, as well as in Europe around the Black Sea, occurs north (closer to the pole) of the climate type Dfak (though one exception is how the area around Osoyoos in British Columbia in Canada has the climate type Dfao occur north (closer to the pole) of an area with the climate type Dsao, as the climate type Dsao is somewhat rare & geographically constrained to the inland northwestern part of the contiguous US anyway). Most commonly, moving toward the pole or away from large bodies of water, the climate type Dfao transitions to the climate type Dfbo; this occurs to the north in North America & Asia, while in Europe, the climate type Dfbo arises in an area which is both to the north of the climate type Dfao & east of the climate type Dfbk. I could find the climate type Dfac only in the northeastern part of China, specifically around the cities of Shenyang, Changchun, Harbin, and Qiqihar, spanning the latitude range of 41.80-47.35 degrees, and in the US around the city of Aberdeen in South Dakota at a latitude of 45.46 degrees. The climate types Dfac & Dfbo generally transition to the climate type Dfbc further to the north (closer to the pole) in North America & Asia and further to the east (inland) from Europe going into Russia. From those areas, the transitions to the climate types Dflo/Dflc/Eflo/Eflc are less predictable, though the transition from those climate types to the climate type Efld more predictably occurs inland & further to the north (closer to the pole) in Canada & Russia.
The warmer climate types in this set, like Dfao, Dfbo, and Dfbc, are more likely to occur near the east coast of a continent than near the west coast of a continent, and when they occur closer to the east coast of a continent than its more central areas, those areas tend to get more precipitation concentrated in the summer half of the year. (This is also true of the climate type Dfac, though that is very strongly geographically constrained anyway). This is because at similar latitudes, climate types near the west coast of a continent tend to have warmer winters due to the prevailing westerlies consistently bringing mild or cool moist air to moderate the temperatures. By contrast, the climate types transition to Dflo/Dflc/Eflo/Eflc/Efld far enough north (close to the pole) that the air becomes too cold to consistently carry as much moisture and the prevailing westerlies bringing warm moist air from closer to the tropics give way to the irregular polar easterlies bringing cold blasts of air from the pole; any moisture will be more likely to precipitate near the east coast of a continent especially given the persistent but movable low-pressure systems over Iceland (at the boundary of the Atlantic Ocean & Arctic Ocean) & the Aleutian Islands (at the boundary of the Pacific Ocean & Arctic Ocean) arising from the boundary of the Ferrel cell & the polar cell. This is also why those climate types, though seeming to be qualitatively dry in general, are not classified as having the first letter B (arid or semi-arid), just like how any climate type that qualifies as having the first letter F (polar) will be classified as such even if it also qualifies as having the first letter B (arid or semi-arid); dryness comes with coldness, and the vegetation (if present) of those areas has much more to do with the cold conditions than the dry conditions per se.
Efbd
I could only find the climate type Efbd in Russia around the city of Yakutsk, the village of Amga, and the village of Tegyulte at respective latitudes of 62.03 degrees, 60.90 degrees, and 60.15 degrees. These 3 places in Russia are unusual because they are the only places where I could find a climate type with the first letter E (subpolar) and the third letter 'b' or higher; this is because they are far inland (though closer to the east coast of Eurasia) and shielded by mountains from the mild-to-warm moist air from the Pacific Ocean, but the influences of cold air coming from above the Arctic Ocean in the winter as well as intensely cold air from the persistent high-pressure system in the winter half of the year over Lake Baikal in Russia mean that the mean annual temperature is low enough to ensure that the climate type does not have the first letter B (arid or semi-arid) despite very low average precipitation levels each month in an absolute sense. That part of Russia is so sparsely populated outside of the city of Yakutsk that I can't easily find climate data about surrounding areas on Wikipedia.
Climate types with the first letter F (polar), A (tropical), or B (arid or semi-arid)
Very few locations outside of the polar circles have climate types with the first letter F (polar), and those locations tend to be close to the polar circles. Similarly, very few locations outside of the tropics have climate types with the first letter A (tropical), and those locations tend to be close to the tropics. More locations have climate types with the first letter B (arid or semi-arid), but the dryness of those areas means that there still aren't that many human settlements in those areas compared to areas that have climate types with the first letter A (tropical), C (subtropical), D (intermediate), or E (subpolar). This means that I still couldn't get enough locations with climate types with the first letter B (arid or semi-arid) to infer trends in how the second, third, or fourth letters change, other than to broadly say the third & fourth letters decrease closer to the poles and become closer to each other closer to an ocean, and the second letter is more likely to be 's' (semi-arid) than 'w' (arid) closer to an ocean.
Concluding remarks
Ocean warmth
It should be clear by now that cities near the Atlantic Ocean in the northern hemisphere are warmer than cities near the Pacific Ocean in the northern hemisphere, which in turn are warmer than cities near the Pacific Ocean in the southern hemisphere, so these statements can transfer over to the respective oceans themselves. This ordering is because of the Gulf Stream in the Atlantic Ocean in the northern hemisphere and the incursions of the Antarctic Ocean into the Pacific Ocean in the southern hemisphere. Additionally, it should be clear that this is not the same as claiming that cities along the eastern edge of an ocean (along the west coast of a continent) tend to be warmer in the winter than cities along the western edge of an ocean (along the east coast of a continent), whether considering a single ocean or a single continent, or that the ocean along the east coast of a continent is warmer than the ocean along the west coast of a continent; those are general features of all oceans & continents due to the circulation of air & water around the world.
The need for the second letter 's' (dry summers) for climate types with the first letter D (intermediate)
Although climate types with the first letter D (intermediate) and second letter 's' (dry summers) only exist in a few places outside of North America, their prevalence in the central-western part of North America near the west coast shows their utility. Even if this is a function of North America's taller coastal mountains compared to Europe or South America at similar latitudes as well as the Gulf Stream in the Atlantic Ocean making Europe more wet at similar latitudes, these climate type labels are necessary to capture the prevalence of wildfires arising during typically dry summers. This is an important issue that the Trewartha categorization completely misses despite supposedly being built to "fix" the "problems" with the Köppen categorization of the same area in North America.
In principle, my modification to the Trewartha categorization allows for climate types with the first letter E (subpolar) and the second letter 's' (dry summer). This respectively corresponds to the climate types Csc/Dsc/Dsd under the Köppen categorization. In practice, these climate types do not occur for two related reasons. First, if the fourth letter is 'k', then at latitudes where the climate type would have the first letter E (subpolar), areas where this climate type could occur in principle would in practice get too much precipitation through the year (ensuring cool but not cold winters) for the second letter to be 's' (dry summer) due to the prevailing westerlies continuously bringing mild or cool moist air and the subtropical ridge being too far away (closer to the equator). Second, if the fourth letter is 'o' or lower, then at latitudes where the climate type would have the first letter E (subpolar), the air is too cold to hold much moisture even in the winter, so there is not a big enough relative difference between precipitation amounts in the summer & winter halves of the year for the second letter to be 's' (dry summer). For reasons related to these and to the lesser rate of evapotranspiration when the temperature is lower through the year, it is rare for climate types with the first letter E (subpolar) and the fourth letter 'o' or lower to transition to climate types with the first letter B (arid or semi-arid).
Problems with my modification of the Trewartha categorization
Areas around the cities of Marseille in France, Thessaloniki in Greece, and İstanbul, Eskişehir, Ankara, and Bursa in Turkey all have climate types with the second letter 'f' under my modification of the Trewartha categorization (with the first letter being C (subtropical) or D (intermediate) in each case), whereas they would have the second letter 's' under the Trewartha categorization (with the first letter being C (subtropical) or D (intermediate) in each case) and under the Köppen categorization (with the first letter being C (subtropical) in each case). All of these places have notably dry summers and are prone to wildfires, yet my modification of the Trewartha categorization does not capture this. This is because unlike climate types in the southwestern & south-central parts of Europe as well as in the northwestern & southwestern parts of the US, these places generally feature more than one local maximum & more than one local minimum in average monthly precipitation over the course of a year; on top of this, some of them have fewer than 3 months with averages of at most 40 millimeters of precipitation (though the third-driest month may be very close to that threshold), and some of them have the wettest month of the year in September (the last month of the summer half of the year in the northern hemisphere). Additionally, with the exception of Marseille in France, these places are farther from the Atlantic Ocean per se (i.e. farther from the westernmost points in Eurasia), so while they are affected by the subtropical ridge in the summer & the Gulf Stream in the Atlantic Ocean, their greater distance as well as the presence of more small hills & mountains on different sides make precipitation patterns somewhat less predictable; similar effects occur in the inland parts of the states of Washington & Oregon in the US, though there is still a clear enough trend of dry summers in those areas for the climate types to be Dsak/Dsao/Dsbo/Dslo. I suppose that I could further modify my modification of the Trewartha categorization to be more in line with the Köppen categorization with respect to the conditions for the second letter to be 's' (dry summer) with the first letter being C (subtropical) or D (intermediate), but this seems like a cheap post-hoc fix. Instead, I'd rather accept deficiencies in my modification of the Trewartha categorization in these areas. In particular, I would be willing to accept agreement in at least 2 out of the 3 climate classification systems that I've considered (the Köppen categorization, the Trewartha categorization, and my modification of Trewartha categorization). This means that the Trewartha categorization & my modification of it (leaning more to the latter because of the mandatory use of third & fourth letters) do better than the Köppen categorization in the Mid-Atlantic & Northeast regions of the US as well as in some parts of the state of California in the US (particularly near the cities of Bakersfield, San Bernardino, and Riverside), the Köppen categorization & my modification of the Trewartha categorization (leaning more to the latter because of the distinction between the first letter C (subtropical) and D (intermediate) in different climate types under my modification of the Trewartha categorization) do better than the Trewartha categorization (due to the use of the second letter 's' (dry summer) when the first letter is C (subtropical) and D (intermediate) under my modification of the Trewartha categorization) in the Northwest region of the US (despite, ironically, the Trewartha categorization being created to "fix" the "problematic" climate labels of exactly that region under the Köppen categorization), and the Köppen categorization & the Trewartha categorization do better than my modification of the Trewartha categorization (due to the definition of the second letter being 's' (dry summer) when the first letter is C (subtropical) under the Köppen categorization or when the first letter is C (subtropical) or D (intermediate) under the Trewartha categorization) in some cities in Eurasia along the eastern parts of the Mediterranean Sea.
