Get ready for some bitterly cold temperatures tonight.
The forecast low tonight is 0 degrees in much of northern Illinois, with wind chills as low as -17, according to the National Weather Service Office in Chicago.
Winds are forecast to be between 15 and 20 miles per hour, with gusts as high as 30 miles per hour.
Western counties, including McHenry and DeKalb, are under a wind chill advisory, with wind chills of -15 to -25 expected.
"A wind chill advisory means that very cold air and strong winds will combine to generate low wind chills," according to the National Weather Service. "This will result in frostbite and lead to hypothermia if precautions are not taken. If you must venture outdoors, make sure you wear a hat and gloves."