Record-breaking March heat wave that’s spreading eastward could be one of the most expansive in U.S. history

After smashing March heat records in 14 states and the U.S. as a whole, 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.

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 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, Arizona, with 11 or 12 straight days of temperatures higher than the city’s previous March record, said meteorologist Jeff Masters of Yale Climate Connections.

Gallina said the dome’s eastward movement will mean temperatures in the 90s Fahrenheit (mid-30s Celsius) 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.

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.

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.

On Friday, four places in Arizona and California hit 112 degrees (44.4 degrees Celsius), according to the Weather Service. Not only did that smash the record for the hottest March day in the continental United States by 4 degrees (2 degrees Celsius), but it was only 1 degree 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.

“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 center said.

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.

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 degrees (2.6 degrees Celsius) to the heat, said report co-author Clair Barnes, an Imperial College of London scientist with the group.

The heat dome will move on by late next week, Masters said: “We just have to give it time.”

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—Seth Borenstein, AP Science Writer

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