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A huge heat dome is spreading across the United States and it is shattering March temperature records.
Weather historians say the dome has already smashed statewide March records in 14 states.
Now, the gigantic heat dome that’s baked the Southwest is creeping eastward and may end up being one of the most expansive heat waves in American history, meteorologists and weather historians said.
Experts say the heat wave’s footprint may rival major events in 2012 and 2021.
And it’s not going away for awhile, maybe not till the middle of the next week as April starts, said meteorologist Gregg Gallina of the National Weather Service’s Weather Prediction Center.
“Basically the entire U.S. is going to be hot,” Gallina said on Monday. “The area of record temperatures is extremely large. That’s the thing that’s really bizarre.”
This heat dome — in which high pressure is acting like a pot lid trapping hot air over a region — will leave Flagstaff, Ariz., with 11 or 12 straight days of temperatures higher than the city’s previous March record, said meteorologist Jeff Masters of Yale Climate Connections.
WATCH | What is a heat dome? A climatologist breaks it down:
What is a heat dome? A climatologist breaks it down
Dave Phillips, senior climatologist with Environment Canada, explains what conditions create a heat dome and how ‘oppressive and sultry’ temperatures get locked in for days.
Gallina said the dome’s eastward movement will mean temperatures in the mid-30s C (90s F) by Wednesday over the southern and central Plains. From one-quarter to one-third of the 48 continental states will be flirting with records for March, Gallina said.
How it compares to other record-breakers
The physical area of this heat wave likely dwarfs two other historic heat waves — one in 2012 in the Upper Midwest and Northeast and another in 2021 in the Pacific Northwest — according to weather historian Chris Burt, author of the book Extreme Weather.
It may not be as large as the Dust Bowl heat waves of 1936, but that was a series of heat waves over two months during summer, not a single big event like now, Burt said.
A Los Angeles Dodgers fan covers up from the hot sun during a spring training baseball game against the Athletics on March 21, 2026, in Phoenix, Ariz. (Ross D. Franklin/The Associated Press)
Both the Dust Bowl and the 2021 heat wave were more intense, with higher temperatures that hurt people more because they fell in June and July, Gallina said.
Another saving grace for people in this heat wave is that it’s not as humid as it would be if the temperatures rose in the summer, Gallina said.
Just how hot? And where?
On Friday, four places in Arizona and California hit 44.4 C (112 F), according to the Weather Service.
Not only did that smash the record for the hottest March day in the continental United States by 2 C (4 F), but it was only 1 F shy of the hottest day recorded in the Lower 48 in April.
Climatologist and weather historian Maximiliano Herrera, who tracks global weather records, compiled a list of 14 states that have notched their hottest March day on record since this heat dome started: California, Arizona, Nevada, Kansas, New Mexico, Nebraska, Utah, South Dakota, Missouri, Iowa, Colorado, Wyoming, Minnesota and Idaho.
Depleted water levels are visible at Dillon Reservoir during a season of record-low snow pack as temperatures reach into the 20s C (70s F) in Dillon, Colo., on March 21, 2026. (Cheney Orr/Reuters)
“In Mexico, even May records were trashed with March records broken by as much as 14 (degrees Fahrenheit), far more than July 1936, March 1907 or June 2021,” Herrera wrote in an email.
The National Center for Environmental Information registered at least 479 weather stations breaking records for March from Wednesday through Saturday, based on its network of stations.
Herrera, who analyzed a broader set of data, said the true number is likely higher. Another 1,472 daily records — which are easier to break — were shattered at the same time, the centre said.
What’s causing the heat dome
What’s happening is the jet stream — which moves weather systems from west to east — is pretty much stuck as far westward as the storms dousing Hawaii, where people are seeing torrential rains and flooding, Masters and Gallina said.
WATCH | Hawaii hit with worst floods in 20 years:
Hawaii hit with worst floods in 20 years
A storm brought more than 100 centimetres of rain to Hawaii, causing the worst flooding in 20 years. The floods have forced thousands from their homes, and the National Guard has been brought in to help get people out of the floodwaters.
On Friday, a group of international climate scientists called World Weather Attribution determined that the record heat was “virtually impossible” and 800 times more likely because of climate change from the burning of coal, oil and natural gas. The result of those activities added at least 4.7 F (2.6 C) to the heat, said report co-author Clair Barnes, an Imperial College of London scientist with the group.
The report warned that the heat dome is expected to make snow melt earlier and more quickly in mountain regions in Colorado and California. This could reduce the amount of water available in the summer, leading to increased wildfire danger and risk of water shortages.
The heat dome will move on by late next week, Masters said. “We just have to give it time.”
