Preliminary surveys by the National Weather Service have confirmed at least nine tornadoes touched down in northern Illinois late Monday.
A weather service report says assessments are continuing, and the number of confirmed tornadoes will likely increase.
The report says the tornadoes were caused by one long-tracked supercell thunderstorm.
The heaviest damage was in Coal City and nearby Braidwood, caused by an EF-3 twister, and at a campground in Sublette, caused by an EF-2 tornado.
The weather service says the tornado that hit Coal City had winds up to 160 mph and was the strongest in the Chicago metro area since an EF-5 twister hit Plainfield in 1990.
No deaths or life-threatening injuries have been reported, although the storms severely damaged homes and forced first responders to pull survivors from basements.