The storm is spreading from the Sierra Nevada Mountains and into the Rocky Mountains, bringing rain to lower elevations and heavy snow at higher elevations. The fast-moving storm is expected to move across the Great Plains overnight, where temperatures in the storm’s path are expected to plummet.
The National Weather Service says wind chills in northern Illinois could drop to minus-28 degrees (minus-33 degrees Celsius) by Monday morning. The National Weather Service says the usual low temperature for this time of year in Chicago is 24 degrees.
Winter storm watches also are in effect for the upper East Coast beginning on Sunday night, with heavier snow possible in some areas.