Some 660 flights were canceled at O'Hare International Airport on Thursday due to low visibility brought on by Wednesday night's severe weather, officials said.
Flight delays of up to 90 minutes were reported Thursday night by the Chicago Department of Aviation.
Officials recommend travelers check their airline's website for the status of individual flights.
Storms moved into the suburbs Thursday night.
The aviation department said flights were back to normal at about 8 a.m. Friday morning and no delays were being reported at Midway or O'Hare.