The Chicago Department of Aviation says delays are averaging 20 minutes for flights traveling in and out of O'Hare International Airport.
More than 325 flights have been canceled at O'Hare.
Across town at Midway International Airport, delays are averaging 30 minutes, with no cancellations.
Aviation officials are advising travelers to check their airlines' web site to check the status of flights.
The National Weather Service has forecast snowfall of three to five inches for much of the area.