The center of a low pressure system out of the central Plains is forecast to move over northeast Illinois bringing rain much of the day Monday, then turning colder with snow showers later Tuesday. Arctic-source high pressure will settle over much of the continental U.S. from midweek on. Daytime highs here will hover in the teens to lower 20s, with overnight lows in the single digits to lower teens.

Along the Canadian border, daytime highs will barely make it above zero, with nighttime lows in the minus 5 to minus 15 range. Parts of North Dakota, Minnesota, Wisconsin and upper Michigan will encounter additional wintry weather with snow and freezing rain.

December 2016 averaged 2.5 degrees below normal compared with 11.3 degrees above normal in December 2015.