The swimming season kicked into high gear early in a large swath of the U.S., as a heat wave pushed temperatures into the 90s and beyond on Wednesday in a stretch spanning from northern Florida to the Great Lakes and covering about a third of the country’s population.

The National Weather Service maintained an excessive heat warning through Wednesday evening for most of Illinois, Indiana and Ohio, which have been dealing with the sticky humidity and soaring temperatures since Tuesday.

The heat advisory in place for the Midwest and South stretched all the way eastward to the South Carolina shoreline.

In Fayette County on Wednesday, weather.com listed the temperature high at 94 degrees, but it felt like nearly 100 degrees. On Thursday, it’s predicted to be a high of 92 degrees with the possibility of evening thunderstorms. On Friday, the high is forecasted for 87 degrees.

Then on Saturday and Sunday locally, there will be some relief with highs in the mid-70s, according to weather.com. Next week is expected to return to the 90s.

Meteorologists warned that the high temperatures could be dangerous or deadly for some people and advised residents to stay hydrated, remain indoors if possible and take precautions if they must be outside.

Some of the affected areas were expected to get relief by Thursday. But the hot weather moving out could bring severe thunderstorms Wednesday to Iowa, Wisconsin and points eastward, including Michigan, according to the weather service’s Storm Prediction Center. Those storms could dump large hail or spawn tornadoes or damaging straight-line winds.

Utilities sorted out many of the power outages caused by storms that swept through the Midwest early in the week, but more than 200,000 customers remained without power still as of Wednesday morning, according to poweroutage.us.