Las Vegas sets new March record as historic heat spreads across the U.S. Southwest

A historic March heat event affected the U.S. Southwest on March 19 and 20, 2026, setting a new March temperature record in Las Vegas, Nevada, and a new highest March temperature ever recorded in the United States near Martinez Lake, Arizona. Multiple daily and monthly records were also broken across parts of Nevada, California, and Arizona, while authorities in Phoenix closed some hiking trails because of heat risk. Source