Weather locations in United States of America

The United States is so large that it contains almost every climate type found on the temperate and tropical earth, from tundra in Alaska to tropical reef in Hawaii. Its weather is shaped by a great interior plain that lets cold arctic air pour south in winter and humid gulf air rise north in summer, with mountains on both flanks blocking the oceans.

Main climate types

Four broad zones cover most of the country. The east and south-east are humid subtropical, hot and sticky in summer with rain spread through the year; the mid-continent is humid continental, with cold winters and hot summers; the west is a mosaic of desert, Mediterranean and highland zone regimes; and the Pacific slope is Mediterranean, mild and wet in winter, dry in summer.

Temperatures

The contrast between regions is large. Phoenix, in the Sonoran Desert, averages about 14 °C in January and about 34 °C in July, among the hottest inhabited places in the United States. Chicago averages about -2 °C in January and about 23 °C in July. San Francisco, on the Pacific, averages about 13 °C in both months but is foggy and cool in summer. Miami is near 20 °C in January and 28 °C in July, and Anchorage sits near -3 °C in January and 15 °C in July.

Rainfall

Annual totals run from under 150 mm in the deserts of Nevada and Utah and along the lower Colorado to more than 2,000 mm on the Pacific slope and in the south-east. New York City receives about 1,200 mm fairly evenly, and New Orleans about 1,700 mm with the wettest months in summer. The mountains of the north-west get over 2,000 mm and hold winter snow at altitude.

When to go

The most comfortable months differ by region. The east coast and the south are best in April and May and again in October, avoiding summer humidity and winter cold. The desert southwest is best between November and March, since summer temperatures are extreme. The Pacific coast is pleasant all year, though summer fog can roll in for days. In summer, the northern plains and the Rockies offer relief from the heat; in winter, the ski areas of the Rockies and Vermont have reliable snow.