The National Weather Service issued a Winter Storm Warning for Lake and McHenry counties until midnight.
A Winter Weather Advisory was extended for Cook, DeKalb, DuPage, Kane, Kendall, LaSalle, Will and Lee counties until until midnight.
A Winter Weather Advisory was also issued for Lake and Porter counties in Indiana until 4 a.m.
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A mix of rain, sleet and snow began moving through the area Thursday morning, then switched to full snow in the evening.
The combination led to slick conditions on roads throughout the suburbs. In Mundelein, a school bus collided with as now plow but no injuries were reported. In Glenview, a car crashed into a house.
Many drivers were caught off guard by the conditions.
"Out of nowhere, I don't know if I hit a bump of snow or the wind blew me or something. Something happened, and I did a full 360, and I ended up in the ditch," said driver Kristina Stewart.
Roads went from bad to worse during the evening rush. I-94 just south of the Wisconsin line went from wet to snow-covered in less than an hour.
Snow coats suburbs as winter storm moves through
In Lake Forest, crews hit the streets to salt and plow a clear path through the wet, icy snow. They're well-practiced for winter weather.
"Going back to even the off-season hours, our fleet sections are constantly maintaining the equipment making sure things are ready," said Public Works Assistant Jim Lockefeer.
Officials are warning drivers to be cautious, give plows room and take it slow during the evening commute as the snow continues.
Strong winds, high waves in city as winter weather moves through
The city of Chicago saw icy rain through most of the day, but strong winds were whipping off the lake, creating some impressive waves. The city closed portions of the Lakefront Trail because of a flood advisory along the lakeshore.
The Department of Streets and Sanitation said it has deployed more than 200 salt spreaders in response to the storm, focusing on DuSable Lake Shore Drive and the city's main arterial streets
The Illinois Department of Transportation will also be out in full force, ready for changing conditions across the state, especially with the warm pavement right now.
"As the temperatures start to drop throughout the day and specifically as you get closer to the Wisconsin border, you are going to see a couple of things come into play," Maria Castaneda with IDOT said. "You are going to get a lot more snow versus rain the more north you are as well as in all areas across Chicagoland as the temps start to drop you are going to get a freeze back. So what that basically is, is where you have wet roadways and the temperatures drop and things get more slick."
In Evanston, the conditions may have played a role in a tree falling on several pedestrians on Northwestern University's campus.
The NWS warns of dangerous travel conditions, with winds gusting as high as 35 mph to go with a mix of rain, snow and sleet.
A Lakeshore Flood Advisory is also in effect from 3 p.m. Thursday to 3 a.m. Friday due to waves of 10 to 14 feet in northern and central Cook County and Lake and Porter counties in Indiana, Chicago officials said.
As of 12 p.m., 213 flights were canceled at O'Hare and 119 flights were canceled at Midway. Delays were less than 15 minutes at both airports.
Stick with ABC7Chicago.com and the ABC7 AccuWeather Team for the latest updates on the winter storm.