An arctic air mass sprawling across the eastern, central and parts of the western U.S. on Monday will channel temperatures 20-30 degrees below already historically cold January averages and is poised to slam parts of the South with a disruptive winter storm.

More than 170 million people across the United States, from the Mexican border to the Canadian border are under cold weather alerts ahead of a crippling winter storm expected to sweep through the south from Texas to Georgia,