ERIE, Pa. — Freezing temperatures and below-zero wind chills socked much of the northern United States on Wednesday, even setting a record in a Minnesota city so cold it's called the Icebox of the Nation, and will stay put for days to come as snow-hardened Erie digs out from a record snowfall.Forecasters warned of hypothermia and frostbite from arctic air settling in over the central U.S. and spreading east.The National Weather Service reported International Falls and Hibbing, Minnesota, set record low temperatures on Wednesday morning. International Falls, the self-proclaimed Icebox of the Nation, plunged to 37 degrees below zero, breaking the old record of 32 below set in 1924. Hibbing bottomed out at 28 below, breaking the old record of 27 below set in 1964.Wind chill advisories or warnings were in effect for much of New England, northern Pennsylvania and New York.