Hail damage to cars was expected, according to the National Weather Service, and wind was expected to damage roofs, siding and trees.
Weather radar at 1 p.m. showed a batch of storms heading into Wisconsin from Iowa, moving to the northeast, mostly north of Dubuque.More news: Spanish state prosecutor accuses Jose Mourinho of tax fraud
Periods of scattered showers and thunderstorms, some possibly becoming strong to severe, developed in Chicago's far west suburbs early Wednesday afternoon.
The chance for more storms Thursday and into the weekend remain a possibility.More news: Trump tells senators House health bill 'mean'
Temperatures are forecast to reach into the upper-80s and low-90s with heat index readings of up to 100 degrees. Sunny, with a high near 99. It will be mostly cloudy, with a high near 84 and a northeast wind around 6 miles per hour. Between a half and three-quarters of an inch of rain are possible.
Update 9:20 a.m.: The National Weather Service in Tulsa issued a thunderstorm warning for parts of Okmulgee and Okfuskee counties.More news: Alex Jones interview draws 3.5 million viewers
Also: LaGuardia Airport in N.Y. City hit 101 F on Tuesday, tying the all-time record high for the month (set on June 26, 1952). Thunderstorm chances will continue through Friday morning and into Saturday and Sunday, accompanying a cold front. The low will be around 74.