The National Weather Service's Chicago office issued a wind chill warning for some suburbs, especially west and north, overnight through late this morning, as well as a winter advisory overnight warning of blowing snow.
The warning for Kane, McHenry and DeKalb counties, among others in northern Illinois, says temperatures can fall to as low as 10 below zero in some areas.
Add wind gusts of up to 35 mph, it said, and wind chills will measure as low as 30 below zero through late Thursday morning.
"Frostbite and hypothermia can occur in a matter of minutes," the weather service says.
The winter advisory through 4 a.m. says the wind gusts could create blowing and drifting snow that could reduce visibility in open areas. "Roads may be snow-covered and hazardous," it says.
A wind chill advisory warning against similar cold temperatures is in effect for Cook, DuPage and other southern counties through this morning, as is the weather advisory about blowing snow.