The Highest Temperature Extremes

Greenland Ranch, Calif., with 134°F on July 10, 1913, holds the record for the highest temperature ever officially observed in the United States. This station was located in barren Death Valley, 178 ft below sea level. Death Valley is about 140 mi long, 4 to 6 mi wide, and oriented north to south in southwest California. Much of the valley is below sea level and is flanked by towering mountain ranges with Mt. Whitney, the highest landmark in the 48 conterminous states, rising to 14,495 ft above sea level, less than 100 mi to the west. Death Valley has the hottest summers in the Western Hemisphere, and is the only known place in the United States where nighttime temperatures sometimes remain above 100°F.

The highest annual average (1971–2000 mean) temperature in the United States is 77.8°F in Key West, Fla. The highest summer (June–August) average temperature, 98.2°F, is Death Valley, Calif. The highest winter (December–February) average temperature is 70.2°F for Key West, Fla.

Amazing temperature rises of 40° to 50°F in a few minutes occasionally may be brought about by chinook winds.1

1. A warm, dry wind that descends from the eastern slopes of the Rocky Mountains, causing a rapid rise in temperature.