A Hazardous Weather Outlook was issued late Saturday morning for portions of Northeast Illinois and Northwest Indiana for Saturday afternoon and night, weather officials said.
The National Weather Service said significant thunderstorms were expected.
A tornado watch was issued for parts of north central Illinois and southern Wisconsin from 1:45 p.m. to 8 p.m. Officials said winds could reach up to 70 mph with large hail events to 1.5 inches in diameter.
Officials warn people to head indoors once thunder starts and have multiple ways to hear possible warnings.
As of 2 p.m., conditions were wet and breezy at Midway Airport, and temperatures registered at 69 degrees.