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

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.