The victim, whose name was not released, was hospitalized in critical condition Friday after the tree toppled on him on the city's Northwest Side, the Chicago Sun-Times said.
The storms disrupted commuter rail service and knocked out power to more than 150,000 homes -- leaving about 35,000 customers without electricity by dawn Saturday. ComEd said.
The storms were expected to bring some relief from oppressive heat that enveloped the Chicago region this week, the Chicago Tribune said.
Wisconsin business offering 'therapeutic cuddling' forced to close
Exploding whale video goes viral on Internet