A winter storm could dump between 5 and 7 inches of snow on Chicago and the suburbs. Chicago could get 6 inches or more.
It's part of a storm that started dumping heavy snow on Minnesota and North Dakota Monday night.
A Winter Storm Warning goes into effect at 3 a.m. Tuesday until midnight on Wednesday morning for Cook, DuPage, Kane, Lake and McHenry counties in Illinois. The southern suburbs and Northwest Indiana are also under the winter storm warning.
Light snow late Monday night will become heavier by Tuesday morning. That means both of Tuesday's commutes could be affected, though ABC 7 meteorologist Jerry Taft predicted the heaviest snow wouldn't fall until after 10 a.m.
"Once the snow begins, it's most likely not going to stop," said ABC 7 meteorologist Tracy Butler.
"Both rush hours would be impacted, but the afternoon/evening commute will be much worse," Butler said.
Snowfall is expected to linger into Wednesday morning.
Both Chicago Streets and Sanitation and IDOT were getting their crews ready on Monday for the impending storm. Clearing the roads Tuesday is expected to be a challenge as much of the snow may come during the evening rush hour.
Airlines cancel flights ahead of storm
More than 600 flights scheduled for Tuesday were canceled on Monday in anticipation of the storm.
Those stranded in Chicago because of the snow can take advantage of the blizzard rate at the Hyatt Regency McCormick Place, where the price of a deluxe guestroom has been reduced price to $89.
United Airlines was offering passengers whose flights may be impacted by the winter storm both in the Midwest and Northern Plains the chance to reschedule their flights without additional charges online at united.com.
Airline passengers should check their flight status before heading to the airport. ABC7's Flight Tracker