March 2026 is now officially the warmest March on record for the United States, and it was not close. More than 15,000 location heat records were set or broken during the month, including over 3,000 all-time March records [1]. Seven entire states — Arizona, Nevada, New Mexico, Utah, Colorado, Oklahoma, and Texas — recorded their hottest March in history [2].

The peak arrived on March 20, when a weather station near Martinez Lake, Arizona, hit 112 degrees Fahrenheit, shattering the previous all-time national March record [3]. Southern California recorded 108 degrees the same day. Temperatures ran 20 to 30 degrees above normal across a vast swath of the western and central United States for nearly two weeks.

The World Weather Attribution project, which conducts rapid analyses of extreme events, published its findings on March 20: heatwaves of this magnitude in March are "virtually impossible without climate change" [4]. The study found that human-caused warming made the event at least four times more likely and significantly more intense.

The consequences extended beyond discomfort. Western snowpack, critical for summer water supply, melted weeks ahead of schedule. Las Vegas averaged 6.3 degrees above its previous warmest March — not a record broken but obliterated [5]. Austin, Texas, recorded seven days at or above 90 degrees in a single March, an all-time record.

Spring arrived like summer. The data says this is the new baseline.

-- Dara Osei, London