The climate of the U.S. is as varied as its landscape. In northern Alaska, tundra and arctic conditions predominate, and the temperature has fallen as low as minus 80 °F (-62 °C). On the other end of the spectrum, Death Valley, California once reached 134 °F (56.7 °C); the second-highest temperature ever recorded on Earth.

Mount Hood, an active volcano in the northwest.

On average, the mountains of the western states receive the most snow and are one of the snowiest places on Earth. The greatest annual snowfall level is at Mount Rainier, in Washington, at 680 inches (1,727.2 cm); the record there was 1,122 inches (2849.8 cm) in the winter of 1971–1972. Other places with significant snowfall outside the Cascade Range are the Wasatch Mountains, near the Great Salt Lake, and the Sierra Nevadas, near Lake Tahoe. In the east, while snowfall does not approach western levels, the region near the Great Lakes and the mountains of the northeast receive the most. Along the northwestern Pacific coast, rainfall is greater than anywhere else in the continental U.S., with Quinault Ranger in Washington having an average of 137.21 inches. Hawaii receives even more, with 460 inches measured annually on Mount Waialeale, in Kauai. The Mojave Desert, in the southwest, is home to the driest locale in the U.S.—Yuma Valley, Arizona, with an average of 2.63 inches of precipitation each year.

Wasatch Range, in Utah, part of the Rocky Mountains, next to the Great Salt Lake. Mark Twain described the two as America's Great Wall and Dead Sea.

In central portions of the U.S., tornadoes are more common than anywhere else on Earth and touch down most commonly in the spring and summer. Deadly and destructive hurricanes occur almost every year along the Atlantic seaboard and the Gulf of Mexico. The Appalachian region and the Midwest experience the worst floods, though virtually no area in the U.S. is immune to flooding. The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have decimated the Anasazi people.