Heat warnings and advisories have been posted in more than 14 states Monday.
The hot humid weather is expected in the Southern and Central Plains through parts of the Southeast. Moist air and strong daytime highs near the century mark will create dangerous heat conditions during the afternoon.
Just three weeks into the summer season, temperatures in parts of Oklahoma have climbed to more than 100 degrees for more than 12 days.
Wichita Falls, Texas has spent 36 of the past 38 days in the triple digits.
In Milwaukee, organizers were forced to cancel a half marathon after several runners collapsed.
"For me, it's too hot. At five-miles, I see some passed out. It's very hot," said Julius Kosgei, the winner of the half marathon.
It's predicted the hot weather will also threaten the nation's crops.
"The U.S. forecast is a little more threatening today," Dax Wedemeyer, a broker at U.S. Commodities Inc. in West Des Moines told Bloomberg News. "Heat will rob yield potential from crops."
Forecasters have predicted the dangerous heat wave will move east.
Missouri River Levees Expected to Fail
Meanwhile, it's a different story in some parts of Missouri, where homes, businesses and even a casino are underwater.
Experts say more Missouri River levees are likely to fail this summer because of months of high water and pressure on the system.
Engineers who have studied past floods say the earthen levees in rural areas are at greater risk.
"Most of the levees are agricultural levees. They're not engineered. They're just dirt piled up," said David Rogers, an engineering professor at Missouri University of Science and Technology.
The Army Corps of Engineers predicts that the river will eventually rise high enough to flow over some 18 to 70 levees, mostly in rural areas of southeast Nebraska, southwest Iowa and Missouri.
The rising river threatens several hundred thousand acres of rich Midwestern farmland and even some urban areas.