Heat dome traps dangerous temps, humidity over much of Midwest

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling temperatures and uncomfortable humidity to millions.

The heat will be particularly worrisome this weekend across wide stretches of Nebraska, Illinois, Wisconsin, Missouri and Iowa, where forecasters are warning of extreme temperature impacts.

A heat dome occurs when a large area of high pressure in the upper atmosphere acts as a reservoir that traps heat and humidity, said Ricky Castro, a National Weather Service meteorologist in Illinois.

According to the NWS Weather Prediction Center, daytime temperatures will be in the 90s and overnight temperatures will only drop to the mid-70s from the Great Lakes to the East Coast during the heat wave that’s expected to last into next week.

Moisture blown northward from the Gulf of Mexico is fueling the muggy weather, said Jacob Asherman, a Weather Prediction Center meteorologist. This influx of moisture is fairly typical during late spring and summer, he said.

The heat will be widespread into next week. On Friday, Denver could reach 100°, according to the weather service. Chicago temperatures could reach 96 on Sunday. On Tuesday, Washington, D.C., could see a high of 99 and New York Central Park could reach 96.

Several states in the Midwest could see dangerous temperature impacts over the weekend, according to a weather service measure that rates the risk from zero to four. Parts of Nebraska and Kansas will be in the highest category on the scale on Saturday, meaning that anyone without effective cooling or sufficient hydration could face health risks. On Sunday, Iowa, Wisconsin, Missouri and Illinois also see a category 4 rating.



(AP Photo Jeff Roberson)