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.

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.

Meteorologists were left speechless Tuesday as record amounts of snow fell along the Gulf Coast. Here’s why it was so snowy.