It’s consistently hot during the summer in the U.S. Southeast, but even for Florida and the Carolinas, the intense heat wave expected over the weekend and into the following week is unusual.

The National Weather Service has issued heat advisories across a substantial portion of the East Coast, from central Florida to Virginia, for most of the weekend. Central Florida is expected to see highs reaching the upper 90s F (mid 30s C), with heat indexes hitting between 105 degrees F to 110 degrees F (40.6 C to 43 C). A similar forecast extends through Georgia, the Carolinas, and into Virginia.

Eastern North Carolina is under extreme heat warnings, reaching as far inland as Raleigh and even into a part of South Carolina, including Myrtle Beach. Forecasters are cautioning about dangerously high temperatures, which could approach or exceed 100 F (38 C) in certain areas on Sunday, with heat indexes potentially climbing to 115 F through the evening.

“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. the weather service advised. “Take extra precautions when outside. Wear lightweight and loose fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke. Stay cool, stay hydrated, stay informed.”

The weather service said several major metropolitan areas in the Southeast — including Raleigh and Charlotte in North Carolina, Greenville-Spartanburg in South Carolina, and Atlanta in Georgia — were expected to face an extreme heat risk for several days, with minimal overnight relief. It said over 30 million people would likely be affected at the peak of the heat wave through midweek.

A hot, humid weekend was also in store for the Midwest. Extreme heat watches were out for eastern Nebraska, western Iowa and southern Minnesota. Heat indexes were expected to reach 96 F (36 C) on Saturday and go even higher on Sunday in Minnesota.

And an extreme heat warning was out for the St. Louis, Missouri, area through Tuesday evening, with highs around 99 F (37 C) and heat indexes around 110 F forecast for Monday and Tuesday.

Parts of Iowa were hit by storms Saturday morning that dumped between 2 and 5 inches (5 to 13 centimeters) of rain in some areas and triggered flash flood warnings.