CHICAGO (AP) — The National Weather Service is warning of wind chills between -15 and -30 degrees below zero in parts of northern and central Illinois.

The weather service issued wind chill advisories through Wednesday morning. The temperature Wednesday morning was -2 in Lincoln in central Illinois and -1 at Chicago’s O’Hare International Airport. Weather service forecasters warned of frost bite and hypothermia if precautions aren’t taken, like dressing in layers, avoiding prolonged time outside and bringing pets indoors.

The frigid weather prompted many municipalities to open warming shelters. In Springfield, the Henson Robinson Zoo canceled its Winterland Holiday Zoo Lights on Tuesday and Wednesday due to the extreme cold.

The weather service in Chicago said the cold would ease slightly Thursday and Friday but return Saturday and through the weekend.