For a long time, I had wondered why the climates of San Francisco, Sacramento, and Los Angeles are so different from those respectively of Richmond, DC, and Atlanta. I had read a few articles on Wikipedia on occasion, so I got a sense that it has to do in part with different ocean currents; this made sense to me, as I had become very comfortable (growing up in the DC area) with the warm waters at beaches along the East Coast in the summer, and I was always surprised by the comparatively much colder waters at beaches along the West Coast whenever I'd visit California even in the summer. I knew though that this wasn't the whole story, and I was surprised to see, for example, that even in South America, South Africa, Western Europe versus East Asia, and Australia, there were very similar contrasts in climates between cities along west versus east coasts in the middle latitudes. This made me more curious about the reasons for these similarities, so I recently went down a rabbit hole of Wikipedia articles to learn more and form an intuition about why different places have different kinds of climates. Follow the jump to see my explanation. 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. I'm just putting this out there in case this intuition is helpful to anyone else as a starting point to learn more (and I recognize that an incorrect initial intuition could hurt rather than help when trying to learn more).
Hemispheres
The relevant hemispheres for this discussion are the Northern & Southern Hemispheres. Additionally, the term "summer hemisphere" refers at a given time of year to whichever hemisphere is experiencing summer and the term "winter hemisphere" refers similarly to whichever hemisphere is experiencing winter.
Continents
It will be useful to consider the contiguous continents. These are America (combining North, Central, and South America), Afroeurasia (combining Africa, Europe, and Asia), Australia (focusing primarily on the country of Australia as that is the dominant landmass there), and Antarctica.
Temperature gradients, pressure gradients, and winds
Air will tend to move from hot to cold at equal pressure. Air will also tend to move from high pressure to low pressure at equal temperature. This motion of air can lead to wind at the surface or at higher altitude.
Water vapor, precipitation, altitude, mountains, and deserts
Air is partly composed of water vapor, which is just water in its gas
phase, and that water vapor contributes a partial pressure to the total
pressure of the air. At equilibrium, meaning that the rates of
evaporation & condensation are equal, the pressure of water vapor will increase with increasing
temperature (irrespective of the presence of nitrogen, oxygen, and other elements or
compounds that make up the air, so while it is a convenient shorthand to say that the air can "hold" or "absorb" more water, this is technically incorrect, though arguably harmless in the context of developing intuition about climate); in the context of air (which is not at equilibrium), increasing temperature means that more water can evaporate into the air before reaching that equilibrium partial pressure, implying that the air is more
humid/moist, while cooling such air forces
precipitation (as rain or snow depending on the temperature).
As air rises, it tends to cool. (The reverse of this phenomenon is known as a temperature inversion and leads to smog in populated areas with lots of particulate emissions.) This is common as air approaches a mountain. If this air has a higher moisture content, that will lead to more precipitation on the windward side of the mountain, which is the side of the mountain that the air approaches; on the other side, called the leeward side, the air may have less moisture or may be completely dry, so lands on the leeward side will be relatively more dry even if lands on the windward side experience precipitation. In cases of extreme heat or mountain heights, especially if mountains fully surround a land, that land may become a desert.
Pressure, density, and moisture
When air is warm, it tends to rise. This rising air creates something like a vacuum below, which reduces the overall pressure there. Another way to see this is that at a constant warm temperature, rising air has less density than air that isn't rising, so by the ideal gas law \( p = k_{\mathrm{B}} TN/V \) where \( N/V \) is the number density, a reduction in density at constant temperature near the surface reduces the pressure. Alternatively, at constant pressure, if the temperature increases, the density must decrease, and less dense fluids tend to rise above more dense fluids. For the same reason, when air is colder, it tends to fall. This falling air compresses air below, which increases the overall pressure there as at constant temperature, an increase in density leads to an increase in the pressure, or at constant pressure, a decrease in the temperature leads to an increase in density and more dense fluids tend to fall below less dense fluids.
At equal temperatures, water with more moisture will have less pressure than water with less moisture. This is because the density of moist air is less than the density of dry air. (To understand this, note that the mass density of water is less than that of the mass density of diatomic oxygen or nitrogen, which are the main components of air, so replacing a little of those elemental molecules with water will reduce the overall density.) This is why air pressures are usually higher over land than over oceans, rainstorms are low-pressure systems, and high-pressure systems over land usually correspond to dry weather (at any temperature).
As I understand, at high altitudes, because the air is generally less dense and has less air above to create pressure, temperature differences are more significant drivers of winds than pressure differences, whereas at low altitudes (near the surface), the greater amount of air above means pressure differences have a greater likelihood than at higher altitudes to drive winds. However, I could be wrong about this intuition.
Coriolis effect
The Earth rotates from west to east, which is why in any location (outside of the polar regions), the sun rises east of its highest point and sets west of its highest point. As air in the atmosphere & water in the oceans are fluids, they won't be completely rigidly dragged with the Earth's rotation; that inertia from the perspective of someone rigidly rotating with the Earth means those winds & oceans look like they are moving from east to west. This is the Coriolis effect, and it significantly affects global wind patterns & ocean currents.
Global Ocean Currents
In both hemispheres, the ocean's water will be hottest near the equator and will move from east to west due to the Coriolis effect; the exact latitude of this band of east-west motion will deviate by up to a few degrees of latitude away from the equator into the summer hemisphere. When this water hits the east coast of a continent (on the western side of the ocean), some will go toward one hemisphere and some will go toward the other hemisphere, and this would happen as spontaneous symmetry breaking even in the absence of explicit symmetry breaking from being in the summer hemisphere or from an asymmetric shape of the continent. For the rest of this section, only one hemisphere can be considered, as the behavior in the other hemisphere is exactly analogous. When the water hits the east coast of the continent and goes into one hemisphere, it tends to roughly follow that east coast toward the pole until about 60 degrees in latitude, cooling along the way, at which point it diverges and starts moving from west to east at a cooler temperature. It will continue moving until it hits the west coast of another continent, at which point it will start moving back toward the equator along that west coast, warming along the way, until it rejoins the water moving from east to west along that band near the equator, completing the cycle. This motion is heavily influenced by winds too and by gradients in salinity, but I have less intuition for how those factors affect ocean circulation and climate in turn. This leads to the major global ocean gyres; these cycles go clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. That said, there are other major & minor ocean currents that I'm glossing over.
Global Wind Patterns
Hadley cell: rising warm air at the equator, falling cold air at the subtropical ridge
Just like the ocean currents, air over the oceans will be consistently warmest around the equator, deviating by a few degrees of latitude into the summer hemisphere, and will move from east to west due to the Coriolis effect. This warm air will rise, creating a low-pressure band near the equator.
As the air rises, it will be driven by the temperature gradient into each hemisphere toward the pole. The air, once cooled, will begin to fall to the surface around 30 degrees in latitude, forming a high-pressure band known as the subtropical ridge. The cooler air at the surface at higher pressure will be drawn toward the equator at lower pressure. This forms the trade winds, which flow from the northeast toward the equator in the Northern Hemisphere and from the southeast toward the equator in the Southern Hemisphere. This cycle is known as the Hadley cell.
Polar cell: falling cold air at the pole, rising warm air at the polar front
Air will be consistently coldest at the poles. This cold air falls, creating consistent high-pressure systems known as the polar highs, and at the surface, this air moves toward the equator drawn by lower pressure. This surface air moves toward the west because of the Coriolis effect and these winds are known as the polar easterlies. As the air warms, it begins to rise around 60 degrees in latitude, creating that low-pressure band known as the polar front. At higher altitude, the relatively warmer air is then drawn toward the pole, completing the cycle. This cycle is known as the polar cell.
Ferrel cell: between the Hadley cell and polar cell
The subtropical ridge around 30 degrees in latitude will be higher temperature and possibly higher pressure than the polar front around 60 degrees in latitude. It is clear that at the surface, the pressure difference will drive winds toward the poles, and the fact that air falling at the subtropical ridge moves from west to east (as would have to be the case to complete the cycle for the Hadley cell) means that air at the surface will move from the subtropical ridge to the polar front from west to east; these winds are known as the prevailing westerlies. However, I'm not exactly sure how the cycle would be completed when the air rises at the polar front if it is colder than the subtropical ridge even at higher altitude. In any case, the cycle is usually completed, yielding the Ferrel cell between the Hadley cell and polar cell. The prevailing westerlies flow from the southwest to the northeast in the Northern Hemisphere and from the northwest to the southeast in the Southern Hemisphere, bringing warmer air from points closer to the equator to points closer to each pole. That said, because the polar front is not directly heated like the equator and the subtropical ridge is not directly "cooled" like the poles, the Ferrel cell is much weaker than the Hadley & polar cells, and the prevailing westerlies are much more prone to disruption than the trade winds or polar easterlies. This susceptibility to disruption can explain a lot of the more variable weather patterns in the middle latitudes (30 to 60 degrees in latitude).
Using these principles to explain actual climates
Equator to 15 degrees in latitude in each hemisphere
It is easiest to start with the most consistent part of the Hadley cell. Near the equator, the trade winds and the warm ocean currents flow in the same direction. Thus, up to 15 degrees in latitude in each hemisphere, lands have tropical rainforest or savanna climates with consistently hot weather & lots of rain. This can be seen in America (especially Central America and South America within those latitudes) and Afroeurasia (especially Africa within those latitudes along with the Southeast Asian island nations). There are two notable exceptions that I see. One is the Atacama Desert within those latitudes; this is easy to explain by the north-south Andes Mountains blocking the warm moist air from the east getting to the west. The other comprises the lowland deserts of Somalia & Kenya; this is harder to explain, as those are on the east coast and not elevated, so they should be getting a lot of warm moist air, and I'm not sure why they are deserts (unless they are getting much more dry air from the deserts of the Arabian peninsula).
15 to 30 degrees in latitude
The subtropical ridge throughout the year can extend in the range of 15-30 degrees in latitude, so the trade winds will still go from east to west but will come more from the subtropical ridge farther from the equator instead of exactly aligning with a specific latitude. Meanwhile, the warm ocean currents start to flow away from the equator toward the pole (going from warm to slightly cooler) along the east coast of a continent or toward the equator away from the pole (going from slightly cooler to warm) along the west coast of a continent. Thus, as the trade winds move from east to west across a continent, they will lead to the continent being, at & near the east coast, consistently warm for several months with consistent rain through the year from the warm waters (like in Florida, eastern Texas in the US, the East Coasts of Mexico, Brazil, Mozambique, Madagascar, South Africa around Durban, and Queensland in Australia, and Southeast Asia), then, more inland, warm but a little more dry with more dependence on a monsoon (like a little more west of the east coasts of Texas in the US, Mexico, South Africa, and Queensland in Argentina, Lesotho, most of India & Bangladesh, and northern Argentina), and finally, in the western portion up to the west coast, desert (like in northern Mexico from the interior to the West Coast (except for Puerto Vallarta due to specific local wind patterns & water coming from the ocean to its southwest), northwestern Argentina & Chile in the Atacama Desert at those latitudes, the Sahara desert, the deserts of Southwest Asia including the Arabian peninsula, most of northern South Africa along with Botswana & Namibia, and most of Australia).
60 degrees in latitude to pole
Next, it makes the most sense to consider the polar cell, which is consistent like the Hadley cell. Around 60 degrees in latitude, the polar easterlies, going from east to west, move in the opposite direction of the major ocean gyres, going from west to east. This could potentially lead to stronger storms, and those latitudes will be consistently cold in the winter & at best mild in the summer, but I'm not sure what the pattern is for precipitation beyond more local effects and beyond coastal locations getting more consistent rain than inland locations (which will be tundra). As I understand, the polar high extends from the pole to 75 degrees in latitude, so in those parts of America & Afroeurasia as well as the ice sheets of the Arctic Ocean, as well as in Antarctica, the weather is consistently dry & very cold. From 60-75 degrees in latitude, there is more room for low-pressure systems to exist as long as there is enough surrounding ocean, which is the case in many parts of the Northern Hemisphere, so small islands as well as coastal areas will be fairly cold, but that cold will be somewhat moderated by significant consistent moisture, while inland areas in the continents will be much more cold & dry; in the Southern Hemisphere, this latitude range is taken up almost entirely by the continental landmass of Antarctica, so those lands are much more likely to be much more cold & dry, with only a few places along the coasts further from the poles (and in smaller islands) that are more moderately cold & wet.
45 to 60 degrees in latitude
From 45-60 degrees in latitude, the main winds are the prevailing westerlies, and ocean currents along a west coast go from 60 to 45 degrees in latitude going from cool to slightly warmer in the process, while ocean currents along an east coast go from 45 to 60 degrees in latitude going from slightly warmer to cool in the process. From west to east, the continent will have, at its west coast, consistently mild summers & winters with consistent rainfall through the year (as in the panhandle of Alaska in the US, coastal British Columbia in Canada, Northern Europe, the British Isles, and France) due to the consistently cool ocean currents along the west coast, then, in the interior, more dry conditions with more extreme high & low temperatures (as in the interior provinces of Canada, Kazakhstan & the parts of Russia immediately to its north, and Mongolia & the parts of Russia immediately to its north), and finally, closer to & on the east coast, consistent rain throughout the year but in more sporadic intense storms from local ocean breezes (with the ocean water being slightly warmer) colliding with dried-out prevailing westerlies & other winds with temperatures being more extreme than on the west coast (due to the ocean current diverging from the east coast) but (due to the moderation of the ocean with higher specific heat capacity than dry air) less than in the interior (as in the Maritimes in Canada and the Kamchatka peninsula in Russia). There are no examples from the Southern Hemisphere as the only major continental land in that range of latitudes is the strip of land in South America that is too narrow for these trends to be observed, but the cities of Hobart & Melbourne in Australia as well as Gqeberha in South Africa have climates more like Vancouver or Paris, despite the former set of cities having latitudes in the range of 35-40 degrees (as opposed to 45-60 degrees), as those cities are on the south coasts of their respective continents & are affected by an ocean current flowing around Antarctica from west to east aligned with the prevailing westerlies (which I glossed over before and which has no analogue in the Northern Hemisphere as those latitudes are mostly taken up by land), so they are cooler & more consistently wet than other cities at the same latitudes of the same continents (like Cape Town in South Africa compared to Gqeberha).
As the prevailing westerlies go in the opposite direction of the trade winds, at these latitudes, dry regions are more likely to be to the east instead of the west; alternatively, regions at the east coast that have mountains immediately to the west may depend more on warm ocean water for summer rain with less rain in the winter (like in Vladivostok in Russia). Areas fully surrounded by mountains & further inland, especially those that are at higher elevations, are more likely to be proper deserts or otherwise consistently dry (like in many parts of Kazakhstan & Mongolia).
30 to 45 degrees in latitude
In the winter hemisphere from 30-45 degrees in latitude, the situation is largely the same as from 45-60 degrees in latitude, with a consistently wet & mild west coast, a significantly more dry & cold interior, and a sporadically wet & moderately cold east coast, with temperatures overall warming when going from 45 to 30 degrees in latitude; this is because the prevailing westerlies, pressure patterns, and ocean currents are qualitatively the same. By contrast, in the summer hemisphere from 30-45 degrees in latitude, things look drastically different because the subtropical ridge, which is usually between 15-30 degrees in latitude in the winter hemisphere, can extend up to 45 degrees in latitude in the summer hemisphere (especially over land because, as mentioned earlier, air tends to be at higher pressure when dry over land than when wet over the ocean); this spreading of the subtropical ridge severely weakens the prevailing westerlies, so the climate over the west coast is dominated by the subtropical ridge, while the climate over the east coast is dominated by local winds, ocean currents, and topography (like mountains). In particular, the east coast, which gets warmer water coming from the equator into the summer hemisphere, would more often get more rain through the year & more humid hot summers with more localized collisions of different air masses (like in the East Coast of the US, Uruguay, Buenos Aires in Argentina, Japan, Shanghai in China, and Sydney in Australia), compared to its counterpart between 45-60 degrees in latitude, as well as slightly warmer winters closer to the equator. The west coast (like in the West Coast of the US, Chile in those latitudes, Portugal, the settlements of Europe around the Mediterranean Sea, Cape Town in South Africa, and Perth & Adelaide in Australia) has even more dramatically different weather in the summer compared to its counterpart between 45-60 degrees in latitude, as the persistent subtropical ridge high-pressure band gives consistently hot dry days with no chance of precipitation, while nights would be cool due to the dry air & winds coming across the cool ocean waters coming from the pole (the latter being more relevant to cities on the coast compared to cities more inland). Only the interior (like the Upper Midwest & Mountain West states of the US, southern Argentina in those latitudes, and West & Central Asia) can still consistently be predicted as dry & temperate, though these features intensify with the spreading of the subtropical ridge over these latitudes. To summarize, in the winter, the range of 30-45 degrees in latitude looks like a warmer version of the range of 45-60 degrees in latitude, with wetness in the west and dryness in the east, while in the summer, the range of 30-45 degrees in latitude looks like a cooler and flipped (horizontally about lines of longitude) version of the range of 15-30 degrees in latitude, with the subtropical ridge leading to dryness in the west and localized sea breezes in the east bringing large but sporadic amounts of moisture analogous to the trade winds (as the subtropical ridge would largely attenuate the prevailing westerlies as they move over land toward the east coast); this flip is perhaps most obvious in Chile when comparing its northern (closer to the equator) and southern (closer to the pole) parts to neighboring countries at the same latitudes.
The effects of highlands, mountains, and deserts are similar for the range of 30-45 degrees in latitude as for the range of 45-60 degrees in latitude. In particular, areas fully surrounded by mountains & highlands are more likely to be deserts or similarly dry (like in the Southwest states of the US and the interior of Spain), while highlands themselves would only be wet if they are on coasts (which is rare, though an example at the somewhat smaller latitude of 25 degrees south would be Curitiba in Brazil).
It is clear that dry air can change temperature in either direction much more than humid air as the greater specific heat capacity of water literally & figuratively damps changes in temperature. Thus, the east coast of a continent will have its highest temperatures in the summer effectively limited by humidity & rain, whereas the west coast of a continent in the summer in the range of 30-45 degrees in latitude can see much higher record high temperatures in the summer, more like a hot desert, compared to the east coast. For cities on or near the west coast in the range of 30-45 degrees in latitude, the extents of summer heat (with dryness being given) & winter moisture (with mild temperatures being given) depend a lot on local topography, especially nearby mountains & deserts; as examples, most cities directly on the West Coast of North America and all cities on directly the coast of Chile have summers that are warm but not hot, while in the US, Los Angeles is the only city directly on the coast that has the combination of higher summer heat and moderate winter rain, as San Diego along with cities in the California peninsula in Mexico have much drier winters, but many cities directly on the Mediterranean Sea in Europe & Northern Africa (with somewhat higher latitudes than Los Angeles) have this combination of hotter summers & moderately wet winters depending in part on the existence of the Gulf Stream bringing warmer waters at higher latitudes along with their positions relative to nearby mountain ranges. That said, cities that are slightly more inland from the west coast, especially those in valleys like the central valleys of California & Chile, more reliably have the combination of hot summers & wet winters (the latter more likely the farther they are from the equator); in particular, the extreme similarity of the geographies of California & Chile, featuring, from west to east, a west coast, a shorter (in height) coastal mountain range, a central valley, and a taller mountain range (respectively the Sierra Nevada or Andes Mountains), means that there are many analogies in the climates of different cities at similar latitudes in either direction, like Valparaíso in Chile & San Francisco in California being directly on their respective coasts at central latitudes, Concepción in Chile & Eureka in California for being in the latitudes slightly closer to their respective poles directly on their respective coasts, and Santiago in Chile & Sacramento in California for being in their respective central valleys. Moreover, cities directly on the west coast could in principle have summer high temperatures that go arbitrarily high due to the subtropical ridge, but this is in practice typically moderated by the sea breezes that would also slightly moderate the high pressure from the subtropical ridge (which is why most such cities have warm but not hot summers), so high temperatures rarely approach records. By contrast, cities that are a bit more inland from the west coast (though not necessarily deep in the interior of the continent per se) have no such moderating effects, so temperatures & pressures can go arbitrarily high, as in the heat domes that sit a little inland of the West Coast of the US in the summer. This is not a binary effect but exists on a spectrum: for example, in the Central Valley of California, Redding has higher temperatures in the summer than Sacramento (in both the daytime & nighttime) despite being closer to the pole because Redding is nestled in the mountains at the northern edge of the Central Valley with very little connection to the Pacific Ocean to the west, whereas sea breezes can flow more easily through the Coast Range mountain passes into Sacramento to make the daytime temperatures slightly more moderate (though still hotter than cities on the coast even closer to the equator, like Los Angeles) & nighttime temperatures much cooler; in Chile, the much shorter heights of & larger number of gaps between the mountains of its Coast Range south of the Atacama Desert means that cities in its Central Valley south of the Atacama Desert are less isolated from the sea breezes, so its cities have more moderate daytime & nighttime temperatures in the summer compared to Redding in California.
Notes specific to the continental US
As I initially thought about this question of climate in the context of the US, I thought it might be useful to note a few other points of interest specific to the US (though I think I've answered my question to my own satisfaction, as I now understand why the climates of San Francisco, Sacramento, and Los Angeles are so different from those respectively of Richmond, DC, and Atlanta). These are as follows. The land between the Gulf of Mexico & the Great Lakes gets a lot more precipitation than would be expected for being so far from the East & West Coasts of the US because of the ocean currents pumping warm water & associated warm moist air through the Gulf of Mexico (leading to sporadic strong storms throughout the year) and the Great Lakes functioning like reserves of moisture & heat. Thus, I find it interesting that the Central Valley in California & the agricultural regions of the Midwest are similarly productive in agriculture despite very different rain patterns, as the Central Valley gets a consistent drizzle only in the winter with less rain on average over the course of a year compared to many parts of the Midwest (especially those further east & directly south of the Great Lakes). Also, as I understand (but I might not be correct about this point), in the summer as the land becomes hotter, localized areas of low pressure from air rising in the Midwest (farther from the coasts) may conflict with the dominant subtropical ridge high-pressure system, so these conflicts when combined with warm moist air drawn in from the Gulf of Mexico may lead to the frequent tornadoes seen in the Midwest (which don't happen to nearly the same extent on any other continent because the land isn't flat enough at those latitudes). Additionally, I was previously aware that Denver in Colorado gets occasional summer thunderstorms, and I now understand that this is from the rare occurrence of warm moist low-pressure systems being drawn all the way from the Gulf of Mexico and colliding with dry air in the dominant subtropical ridge high-pressure system.
Finally, I had wondered why going north along the East Coast of the US leads to climates that necessarily couple milder summers to winters that are more cold & dry instead of allowing the winters to be more mild & wet too, and why climates that have mild summers along with mild wet winters only exist along the west coast of a continent between 45-60 degrees in latitude and not along the east coast between 30-45 degrees in latitude. Now, I understand why: consistent moisture to moderate winter temperatures can only come at those latitudes from the prevailing westerlies coming right off of the ocean onto a west coast, whereas on the east coast, the prevailing westerlies are largely dry, and further away from the equator, the ocean current starts to diverge from the east coast, so winters must become more cold & dry on the east coast as one approaches the pole in this latitude range.
Notes specific to Italy
As I looked on Google Maps, I noticed that while many cities on the West Coast of Italy have climates similar to those of the major cities of California, many cities which are separated from the broader Mediterranean Sea by the Apennine Mountains (and from the rest of Europe by the Alps) and can only face the Adriatic Sea (whether directly on the coast, like Ancona, or a little more inland, like Milan) have climates that contrast with these and are more similar to DC, with more humid summers, colder winters, and moderate precipitation all year in more sporadic strong storms. This further contrasts with cities in the Balkan peninsula on the other side of the Adriatic Sea directly on its coast, like Split in Croatia, which have hot dry summers & mild wet winters, so the Adriatic Sea is somehow a microcosm of an ocean separating two continents even though it is at most 500 miles long & 100 miles wide.
Climate change, at least in the US
This unified understanding of the climate of the US made me wonder how the climates of different parts of the US will change with global warming, in particular referring to warming of the atmosphere and the oceans (along with other major bodies of water), and how to understand such changes in the context of these intuitions about climate. Already, many of the effects are clearer compared to the norms from the previous few decades. The panhandle of Alaska is becoming even wetter, permafrost is melting in the interior of Alaska, and Hawaii may become more dry. Along the West Coast, summers will become longer, hotter, and drier (so in a few decades, the climate of Portland in Oregon may look more like that of Los Angeles a decade ago), leading to more droughts & fires (which are already happening more intensely in the interiors of all of the states of the West Coast), while winters will feature less frequent rains (due to overall drier conditions & longer summers) that will become more intense only in places that already get significant rain (i.e. along the whole coast and in the Sacramento Valley, but not in the San Joaquin Valley, which will become more like a desert as Bakersfield already is). The deserts of the Southwest will become hotter, and the Mountain West states will become hotter & drier, though it isn't clear to me if the latter region could be hit by more frequent or more intense storms from the Gulf of Mexico. The Midwest & South between the Great Lakes & Gulf of Mexico along with the East Coast will see in the summer more intense rain and more days that are hotter than current averages and, in the winter, snow becoming rarer in places where it is already rare (like DC) and more intense in places that already experience the lake effect (like Buffalo) or are in mountains that lead to precipitation (like Roanoke); meanwhile, cities directly on the East Coast will be vulnerable to sea level rise.
This is what turns me away from the temptation of settling in a mountainous inland part of the East Coast, like New Hampshire, Vermont, western Maryland, or southwestern Virginia for the sake of adapting to climate change: the summer temperatures, even if warmer than before, may still be tolerable in an absolute sense where they won't be as tolerable in lowlands, but more intense storms with rain or snow will be more of a problem in these remote areas that are already harder (than lowlands) to serve with infrastructure & public services relevant to such extreme weather events. Thus, from the perspective of adapting to climate change, I'd rather settle in the DC area as it is far enough inland to avoid damage from sea levels rising while maintaining the moderate climate from being closer to the coast, its air conditioning can deal with more days that are hotter than current averages as record high temperatures are unlikely to be significantly exceeded (due to the moderating effects of humidity & rain in the summer), and snow is becoming rarer instead of more intense; it is possible that rain at other times of the year will become too intense for current infrastructure to handle, but that difference between actual rain & infrastructure capacity is much less than I've seen of the difference during the intense rains across the coast of California, the Sacramento Valley, Stockton, and the San Fernando Valley in 2022 December & 2023 January.
