The National Weather Service issued a severe thunderstorm warning and flood advisory for most of Northern Illinois.
The warning was in effect until 4:00 pm, Sunday. Damaging wind and heavy rain were expected, according to NWS.
Delays at O'Hare Airport were an hour or more and over 450 flights have been canceled as of 8:30 pm.
Delays at Midway were at 30-40 minutes.
According to Comed, 4,300 households are without power, 2,500 of which are in the western suburbs.
The severe weather is also causing major flooding throughout the Chicagoland area.
The NWS issued a Flash Flood warning for Northern Cook, Southern Lake, Northern Lee, Dupage, Northern Dekalb, Southern Boone, Southern Winnebago, Ogle, Southern McHenry and Kane counties.