CHICAGO (AP) — Homeless advocates opened warming centers, children bundled in parkas and scarves, and wind-lashed commuters quickened their pace Tuesday as brutal cold gripped Illinois.

Temperatures in northern Illinois fell below zero Tuesday morning for the first time in almost two years, with wind chills as low as 15 to 20 degrees below zero, the National Weather Service said.

Readings across the state ranged from a low of minus 7 in Mundelein, about 50 miles north of Chicago, to 18 degrees in Carbondale, in southern Illinois. A low of 1 degree was recorded at Chicago's O'Hare International Airport just before 8 a.m.