As a winter system threatened to usher in more snow, freezing rain and ice for the Chicago area, more than 700 flights were already canceled and black ice warnings were issued Tuesday.
At O'Hare Airport, at least 602 cancellations were reported as of 4 p.m. At Midway Airport, 99 cancellations were reported.
An alert from the FAA also reported numerous delays at both airports. A traffic management program was in effect for both locations, the FAA reported.
In suburban Aurora, police issued a warning for commuters after receiving an increasing number of calls for crashes and motorists needing assistance.
"Our Officers are saying black ice is forming and roads Citywide are getting slick. The number of calls for crashes and motorist assists are increasing," the department tweeted. "Please be AWARE and please SLOW DOWN. Play it safe and if you don't have to drive, let it wait until tomorrow."
The National Weather Service said it received reports of multiple accidents on Interstate 80 and Interstate 55 in Grundy County and urged commuters to use "extreme caution if you must drive."
Numerous spin-outs and reports of cars in ditches came along I-55 in Joliet.
The Illinois Tollway said it mobilized its fleet of 196 snowplows in response to the freezing rain and snow set for rush hour travel.
“Our trucks are salting the pavement to prevent ice from forming but conditions may vary as the storm moves through the area, so we ask drivers to please slow down and be alert,” Illinois Tollway Executive Director Liz Gorman said in a statement. “We are reminding everyone to allow extra time to complete their trips and give snowplows and emergency vehicles the extra room they need to safely do their work.”
In Boubonnais, School District 53 released students early "due to heavy freezing rain" expected. The district also canceled after school activities and p.m. Pre-K.
"Although this is inconvenient, we feel it is in the best interest of our students' safety for our buses to run at this earlier time," the district said in a statement.
A Winter Weather Advisory began across the Chicago area at 9 a.m. Tuesday and continues through Tuesday evening and Wednesday afternoon for most locations. The timing and precipitation estimates vary across the area (see a breakdown by county here). McHenry County was also under a Winter Storm Warning.
Some locations could see as much as 5 inches of snow mixed with ice accumulations of up to two tenths of an inch before the system comes to an end Wednesday, making travel conditions dangerous for several hours.
"A Winter Weather Advisory means that periods of snow, sleet or freezing rain will cause travel difficulties. Expect slippery roads and limited visibilities, and use caution while driving," the alert states.
The wintry mix comes just days after a snowstorm dumped several inches of snow across the area, with some spots seeing more than 10 inches.
Light snow is expected to develop during the late-morning hours Tuesday and begin mixing with freezing rain and sleet at times.
The icy combination could last for several hours, making for difficult travel conditions before transitioning to rain in southern sections by the evening hours. Snow will continue in far north and northwest counties during the evening hours and overnight, but will likely transition to mainly rain for areas south of Lake, McHenry and Boone counties.
Many areas will likely see a light icy mix changing to all snow again Wednesday morning before ending by the late-morning hours.