Climate of the United States

The climate of the United States varies due to differences in latitude, and a range of geographic features, including mountains and deserts. West of the 100th meridian, much of the US is semi-arid to desert in the far southwestern US, and Mediterranean along the California coast. East of the 100th meridian, the climate is humid continental in the northern areas east through New England, to humid subtropical in the Gulf and South Atlantic regions. Southern Florida is tropical, as is Hawaii and the US Virgin Islands. Higher-elevation areas of the Rocky Mountains, the Wasatch, Sierra Nevada, and Cascade Range are alpine. The West Coast areas in coastal Oregon and Washington are cool oceanic climate. The state of Alaska, on the northwestern corner of the North American continent, is largely subarctic climate, but with a cool oceanic climate in the southeast (Alaska Panhandle), southwestern peninsula and Aleutian Islands.

The primary drivers of weather in the contiguous United States are the seasonal change in the solar angle, the migration north/south of the subtropical highs, and the seasonal change in the position of the polar jet stream.

In the Northern Hemisphere summer the Subtropical high pressure systems move northward and closer to the United States mainland. In the Atlantic Ocean, the "Bermuda High" creates a south-southwest flow of warm, humid air over the eastern, southern and central United States - resulting in warm to hot temperatures, high humidity and occasional thunderstorm activity. In the Pacific Ocean high pressure builds toward the California coast resulting in a northwesterly airflow creating the typical sunny, dry, and stable weather conditions along the West Coast.

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