Rockford broke the record for its all-time lowest temperature Thursday morning when it hit 30 degrees below zero (-34 Celsius).
The National Weather Service says Thursday's temperature at 6:45 a.m. beats the previous record low of minus 27 (-32 Celsius) recorded Jan. 10, 1982.
A cold-weather record was shattered in Chicago too as temperatures reached minus 23 degrees overnight at O'Hare International Airport. That broke the previous daily record of 15 degrees below zero, which was set on Jan. 31, 1966.
The bitter cold that has put much of the Midwest into a historic deep freeze is expected to ease Thursday before snow moves into Illinois.
The snow is expected to begin Thursday afternoon in northern and central Illinois, bringing as much as 6 inches to areas.
It was still frigid Thursday morning, with wind chills dipping to minus 53 in Bloomington.
Transit still was affected too, with about 1,700 flights canceled at Chicago airports Thursday morning and some commuter train lines not running.
Wind chill warnings across Illinois were to expire at 12 p.m. Thursday.