A brutal shift is underway across the United States—and it’s only getting worse. What started as a scorching blast in the Southwest is now expanding fast, pulling millions into dangerous, almost summer-like conditions far too early in the year.

Meteorologists are warning that as many as 23 states will fall under a powerful “heat dome” stretching into the central part of the country. By Friday and Saturday, temperatures could spike up to 30 degrees above what’s normal for late March.

The heat that first gripped California, Nevada, and Arizona is now marching east. States like Texas, Kansas, Missouri, Illinois, and even the Dakotas are next in line, turning what should be mild spring days into something far more extreme.