Some 141 million Americans over nearly 1 million square miles were under a heat alert on Wednesday, the result of a heat "dome" that's only slowly moving away from the central U.S. — and into the East Coast.
The National Weather Service said 22 deaths in recent days were potentially heat related.
"This heat is dangerous on many levels," NWS Director Jack Hayes said in a statement. "Temperatures and humidity levels are high, the heat will be prolonged, and very warm temperatures overnight won’t provide any respite. All of these factors make this an unhealthy situation, especially those in the upper Midwest who are not accustomed to such heat."
Hospitals in Wichita, Kan., treated 25 heat-related illnesses, according to the Weather Service report. In Des Moines, Iowa, 16 people were hospitalized because of the heat.
In Minneapolis, dozens of fans at recent Minnesota Twin games have been treated for heat issues, even though the club did take extra precautions such as providing free water stations and having first aid and guest service staff on hand to monitor crowds.
Day after day of high temperatures and humidity with no relief overnight was taxing the region.
"It's just draining, physically draining," said Chris Vaccaro, a Weather Service spokesman.
At least 27 states were under some sort of heat warning, watch or advisory.
An atmospheric high pressure ridge hanging over the Midwest is blocking moisture, causing a buildup of heat that acts more like a dome than a heat wave. The ridge will weaken by the weekend, permitting cooler temperatures and some rainfall in the Midwest. (more)