The National Weather Service has issued a "hazardous weather outlook" warning motorists and pedestrians of icy and wet conditions as rain continues to fall Saturday and the ground remains colder than the air.
"Although temperatures are above freezing, the cold ground is leading to icy roads across portions of northern illinois. This will continue through this evening," the weather service said just after midnight.
The advisory was targeted at Cook, Lake, McHenry, DuPage, Kane and Will counties, among others in northern Illinois.
Tollway officials earlier warned of standing water on both sides of the Tri-State Tollway near the O'Hare oasis. Illinois State Police were out near the Huntley Road exit of the Jane Addams Tollway on Friday night to tend to an outbreak of potholes that slowed traffic.
The Illinois Department of Transportation's online map showed overnight patches of ice and snow on interstate highways in the Rockford area and west of that city.
The city of Elgin posted on social media late Friday night that its "ice command" had its "A team" out for six hours, watching for slippery pavement.
Forecasters are also warning about possible flooding as the snow dumped on the area over the past several days begins to melt. Meteorologists note that the rainfall exacerbates the melt.
The village of Schaumburg said Friday afternoon via Twitter its snow crews were out salting and two men were working on flood control. Later it said it canceled overnight parking in order to keep the roads clear.
"Schaumburg #police suggest you walk/drive with caution this evening. The rain, slush, ice, and temperature have created slippery conditions," the village tweeted.
Naperville tweeted that crews are ready to help residents with flooding issues. "Report any unusual water build up to City Dispatch at (630) 420-6187," the city tweeted.
Aurora officials dispatched their entire fleet of 34 trucks to salt the 2,100 lanes miles of road the city maintains, according to officials there.
McHenry police issued a hazardous-road advisory, saying there's water on the Dartmoor Bridge and ice on Lillian Strett and the 300 block of Green, WBBM 780-AM reports.
Niles officials warned motorists Friday afternoon that Dempster Avenue at Milwaukee Avenue was closed because of floodwaters.
In Chicago, the Hancock Building was blocked off Friday afternoon with police tape and a sign that read, "Caution, falling ice," ABC 7 reported.