Most of the United States is being assailed with extreme winter weather this week as Arctic air blasts south from Canada, snow tracks up the Northeast coast and a potentially crippling winter storm takes aim at the South.

Around 40 million people, primarily across the southern U.S. from Texas to Florida, were under some type of weather hazard.

A powerful and dangerous winter storm sweeping across the South is dumping heavy snow across Houston and other major metropolitan areas along the Interstate 10 corridor, prompting the first-ever Blizzard Warning along portions of the Gulf Coast.