LANSING, Mich. (AP) - Gov. Gretchen Whitmer has signed an order declaring a state of emergency in Michigan ahead of dangerous subzero weather . Whitmer said Tuesday her move will harness government resources and ensure the public "understands the seriousness" of the once-in-a-generation cold snap. She visited the Cristo Rey Community Center in Lansing - a warming house for residents. Lansing Mayor Andy Schor says the city's homeless shelters are "overloaded." Whitmer has also activated the State Emergency Operations Center to coordinates efforts by state agencies and local governments. Wind chill factors may drop to as low as negative 45 degrees from Tuesday night through Thursday morning. The University of Michigan canceled classes on its Ann Arbor campus Wednesday and Thursday, and Michigan State University suspended Wednesday classes. Some Grand Rapids-area highways were closed Tuesday from pileups. --- This story has been corrected to show that the name of the facility is the Cristo Rey Community Center, not Christo Rey.