Posted Tuesday January 22, 2013 -- at 7:50 a.m.

Police officers in Milwaukee checked under freeway overpasses and other spots to find the homeless and urge them to get out of the dangerous cold and stay at a shelter.

The United Way of Greater Milwaukee has donated $50,000 to help crowded homeless shelters open overflow centers.

To the north in Superior, temperatures dropped to 20 and 30 below zero Tuesday. The wind made those temperatures feel even colder.

Ashland, Bayfield, Hurley, Washburn and Superior are among school districts telling students to stay home Tuesday. Forecasters say with wind chills of minus 20 and below, exposed skin can freeze within a minute.

2012 Copyright: Associated Press