Officials warned residents across the South that the effects of a major winter storm were not over, and that driving remained a hazard on roads frozen with slippery ice.

More than 220 million people across the United States are facing dangerous cold that will also open the door for a potentially historic and crippling winter storm that could deliver snow as far south as Florida and the Gulf of Mexico.

A deep and powerful trough of cold air will drop south from Canada this week, sending temperatures plummeting from the western United States to the eastern seaboard and as far south as the Florida panhandle.