Parts of Cook and DuPage counties, including Chicago, are under a flash flood warning until early Tuesday because of heavy rainfall Monday night.
Up to 2 inches of rain has already fallen on east central Cook County and east central DuPage County as of about 9:30 p.m., according to the National Weather Service office in Romeoville.
Thunderstorms could bring another 1 to 2 inches of rain, and flash flooding is expected, the weather service said.
The flash flood warning lasts until 3:30 a.m. Tuesday, the weather service said. Drivers should especially be careful because it is harder to recognize flooded areas at night.