A wave of severe storms will move across the Midwest and northern Plains throughout the middle of the week, bringing a risk of severe thunderstorms, damaging winds, flash flooding, and possible tornadoes to the area, as Vermont faced "life-threatening" floods after rain soaked the state overnight.

The storms will descend on a broad stretch of the Ohio, Mississippi, and Tennessee valleys on Tuesday afternoon, putting more than 18 million people in Tennessee, Nebraska, Missouri, and Iowa at a slight risk of severe thunderstorms, according to the National Weather Service. More than 19 million were also at a slight risk of a tornado, the agency said.

The Ohio and Tennessee river valleys could see "drenching rain" from a storm complex that moved into the area on Monday evening, according to AccuWeather.

Thunderstorms striking Iowa on Tuesday and Wednesday could have "severe potential," the National Weather Service in Des Moines said on X. The western part of the state and northeastern Nebraska could see damaging winds of up to 75 mph and large hail on Tuesday overnight.

Authorities in Madison County, Iowa, around 40 miles southwest of Des Moines, warned residents that the area was on thunderstorm watch until 5 a.m. on Wednesday, according to a Facebook post. "The winds are fast moving and should be out of here shortly," they wrote.

At the same time, blistering hot temperatures were forecast in the same area, with heat indexes expected to climb above 110 degrees in Omaha and Lincoln. The weather service issued an excessive heat warning through Wednesday evening.

The thunderstorms could drop golf ball-size hail on a swath of central North Dakota on Tuesday evening, with damaging winds of up to 60 mph expected.

Iowa already saw some rainy weather beginning on Sunday – Dayton and Marshalltown, two cities north of Des Moines, both reported more than 3 inches of rain by the next day, the Des Moines Register, part of the USA TODAY Network, reported.

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'Life-threatening' floods sweep Vermont

Meanwhile, Vermont faced "life-threatening" flooding on Tuesday after the northeast part of the state was drenched in up to 8 inches of rain overnight, according to the weather service. People in affected areas should "seek higher ground now," forecasters said on X.

Ten rescue teams dispatched to Caledonia county and Essex county had already carried out around two dozen rescues from the floodwaters, according to a storm update on Tuesday morning from the Vermont Department of Public Safety. Extreme rainfall had washed out roads, creating a dangerous situation.

The Passumpsic River, which runs more than 22 miles through the state, reached 16.4 feet on Tuesday morning, indicating moderate flooding, according to the National Weather Prediction Service.

The weather service ended the flash flood warning at around 10:45 a.m. after the rainfall ended, but urged people to heed road closures and warnings from local officials.

Earlier Midwest storm system caused 27 tornadoes, left 3 dead

The severe weather comes weeks after a dangerous storm system triggered by a derecho pummeled the Midwest, spinning up multiple tornadoes causing flash floods, and leaving multiple people dead. More than 166,000 people throughout the area lost power.

The weather service later confirmed 27 tornadoes touched down in the Chicago area on July 15. A 44-year-old woman in Illinois was killed when a tree fell on her house amid the storms.

Flash floods in Illinois forced hundreds of people to evacuate their homes ahead of the "imminent failure" of a dam and left an elderly couple dead after their car was washed away.

Cybele Mayes-Osterman is a breaking news reporter for USA Today. Reach her on email at [email protected]. Follow her on X @CybeleMO.