The US climate is characterized by wide variations, not just from region to region and season to season, but also day to day and even hour to hour. Even setting aside far-flung Alaska and Hawaii, the main body of the US is subject to dramatically shifting weather patterns, most notably produced by westerly winds sweeping across the continent from the Pacific.

In general, temperatures tend to rise the further south you go, and to fall the higher you climb, while the climate along either coast is, on the whole, milder and more uniform than inland.

The Northeast , from Maine down to Washington DC, experiences relatively low precipitation as a rule, but temperatures can range from bitterly cold in winter to uncomfortably hot (made worse by humidity) in the short summer. Farther south, summers get warmer and longer. Florida 's air temperatures are not necessarily dramatically high in summer, being kept down by the proximity of the sea both east and west. Florida, in winter, is warm and sunny enough to attract visitors from all over the country.

The Great Plains , which for climatic purposes can be said to extend from the Appalachians to the Rockies, are alternately exposed to icy Arctic winds streaming down from Canada and humid tropical airflows from the Caribbean and the Gulf of Mexico. Winters in the north, around the Great Lakes, can be abjectly cold, with driving winds and freezing rain. It can freeze or even snow in winter as far south as the Gulf of Mexico, though spring and fall get progressively longer and milder farther south through the Plains. Summer is much the wettest season in the South as a whole, the time when thunderstorms are most likely to strike. One or two hurricanes each year rage across Florida and/or the Southeast , from obscure origins in the Gulf of Mexico on the way to extinction out in the Atlantic. Tornadoes (or "twisters") are usually a much more local phenomenon, tending to cut a narrow swath of destruction in the wake of violent spring or summer thunderstorms. Average rainfall dwindles to lower and lower levels the further west you head across the plains.

Temperatures in the Rockies correlate closely with altitude; beyond the mountains in the south lie the extensive arid and inhospitable deserts of the Southwest . Much of this area is within the rain shadow of the California ranges. In cities such as Las Vegas and Phoenix, the mercury regularly soars above 100°F, though the atmosphere is not usually humid enough to be as enervating as that might sound.

West of the barrier of the Cascade Mountains, the fertile Pacific Northwest is the only region of the country where winter is the wettest season, and throughout the year the European-style climate is wet, mild and seldom hot. California weather more or less lives up to the popular idyllic image, though the climate is markedly hotter and drier in the south than in the north, and there's enough snow to make the mountains a major skiing destination. San Francisco is kept milder and colder than the surrounding district by the propensity of the Bay Area to attract sea fog, while the Los Angeles basin is prone to filling up with smog, as fog and pollution become trapped beneath a layer of warm air.