In an advisory, the NWS warned that portions of the three states are under flash flood warnings due to expected thunderstorms that will bring heavy rain.

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."

Severe storms moving into the Chicago area are bringing dangerous flash flood threats on Friday afternoon. There is a flash flood warning in effect for Cook and DuPage counties until 2:45 p.m. A ground stop has been issued at O'Hare Airport as storms move into the area.