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."

Nearly 4 inches of rain fell in the Chassell area earlier this week, causing flash floods that washed out roads.