Roughly 40 million people from Texas to the Carolinas are under winter weather alerts as a rare winter storm amid bone-chilling temperatures brings potentially historic snowfall to cities unused to harsh,

Heavy snow, sleet and freezing rain are spreading east across parts of the Florida panhandle and eastern Carolinas, closing roads and schools and grounding flights.

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