A line of fast-moving storms prompted severe thunderstorm warnings in the Chicago area and ground stops at O'Hare and Midway airports. There were also reports of storm damage.

As of 12:30 p.m., heavy rain had already started to fall in some parts. A flash flood warning was in effect for DuPage and Cook County, the NWS said, with reports of "totally submerged viaducts and underpasses in the city of Chicago."