Hottest cities in the US

Most people guess Phoenix, and the Phoenix metro does fill most of the top dozen. But the top spot belongs to Laredo, on the Rio Grande in south Texas, with the lower valley cities of McAllen and Edinburg close behind. South Texas heat starts earlier in the spring and holds later into the fall than desert heat, and it does its work at low elevation under a subtropical sun. Laredo's high reaches ninety degrees on roughly half the days of the year.

The two heat regimes read clearly in the context columns. The Arizona cities pair their hot days with more than three hundred sunny days and fewer than three dozen wet days each year: dry heat under a cloudless sky. The south Texas cities run about sixty fewer sunny days and roughly twice the wet days, because Gulf moisture hazes the sky and feeds storms. That same humidity keeps nights warm and pushes what the air feels like well past what the thermometer reads. A similar count of hot days, a very different experience of them.

Elevation is the quiet variable inside Arizona. Tucson sits more than a thousand feet higher than Phoenix, and that altitude costs it about a week of ninety degree days against Phoenix proper and about three weeks against the hottest Phoenix suburbs, while its sunshine stays nearly identical. It is the standard trade across the Southwest: elevation buys relief from the heat without touching the sun.

The zero end of the table is the marine machinery from the coolest July list working in reverse. Anchorage records no ninety degree days at all, and Daly City and the Puget Sound cities log about one in a typical year. A hot day here is a day whose high reaches at least ninety degrees, the same threshold NOAA uses in its published normals, and the counts come from the station anchored temperature correction described on the data sources page, which restores the threshold day counts that raw model output smooths away.