From Polar Ice to Tropical Reefs
The United States contains examples of nearly every global climate. Alaska reaches into the Arctic, where temperatures have fallen as low as −80°F. Hawaii and southern Florida are tropical, while much of the South is subtropical. California’s coast has a Mediterranean climate, the Great Plains west of the 100th meridian are semiarid, and the Great Basin and Southwest are arid deserts.
This variety is not accidental. The country spans enormous distances and includes mountains, plains, oceans, inland lakes, and islands. Each changes how heat and moisture move through the atmosphere.
The Jet Stream’s Conveyor Belt
A major influence is the polar jet stream, a fast-moving band of air that shifts northward in summer and southward in winter. It carries low-pressure systems from the Pacific toward the continent. The Cascades, Sierra Nevada, and Rocky Mountains strip moisture from these systems, leaving the High Plains much drier.
Over the Great Plains, flat land allows air masses to reorganize. Moisture rising north from the Gulf of Mexico can collide with cold or dry air, producing powerful thunderstorms and tornadoes. In winter, storms may move up the East Coast and intensify into nor’easters.
Rain, Snow, and Desert Air
The Pacific Northwest is exceptionally wet, while the mountains of the West receive extraordinary snowfall. California often has rainy winters and nearly dry summers. The Southwest can experience weeks above 100°F, but summer monsoons from the Gulf of California can trigger severe local thunderstorms.
Florida’s wet summers and dry winters support a major citrus industry. The Great Lakes create lake-effect snow, sometimes burying nearby communities under enormous accumulations.
The result is a national climate mosaic—and a reminder that geography can make one country feel like many different worlds.