The National Weather Service has reported at least five tornado sightings, including three near the city of DeKalb, around 64 miles (102km) west of Chicago.
Wind gusts in excess of 60mph were reported, knocking down trees and light poles and leaving much of the area without power.
There are no reports of casualties.
Experts say an El Nino weather pattern and climate change are at play.
The NWS described Chicago's weather pattern as seeing summer, spring, autumn and winter all "crammed into the next 24 hours".
It described the swing as "absolutely brutal".
Numerous incoming and departing flights at Chicago's O'Hare international airport were delayed, and nearly 30 flights were cancelled as of 22:00 local time (04:00 GMT).
Local media shared footage of hundreds of passengers packing into the airport for shelter.
The Chicago Department of the Environment says the drastic fluctuations in temperature are an example of the unseasonable and unpredictable weather that climate change will continue to bring.
Heavy snowfall, severe thunderstorms and golf ball-size hail have been reported in about a dozen states in the Midwest. People have been advised to stay off the roads.
BBC
