The region's first blast of brutal winter air arrived early Tuesday morning, with wind chills dipping to 15 degrees below zero.
A wind chill advisory is in effect until 10 a.m. in Cook, Will, Lake, LaPorte, Porter, Newton, Jasper and Benton counties.
The National Weather Service warns that cold air and strong winds can cause frost bite and hypothermia if precautions are not taken.
The extreme cold prompted some area schools to delay the start of school by two hours, including Hanover Community School Corp., North Newton School Corp., Tri-Creek School Corp, MSD of Boone Township and Lighthouse Baptist Academy in Cedar Lake.
The cold is also causing problems in the Indiana Toll Road with scattered areas of black ice. Indiana State Police for the Toll Road reported some slide-offs and fender benders, none of which caused serious traffic problems or resulted in serious injuries.