A rare frigid storm charged through Texas and the northern Gulf Coast on Tuesday, blanketing New Orleans and Houston with snow, closing highways, grounding nearly all flights and canceling school for millions of students more used to hurricane dismissals than snow days.

Around 40 million people in the U.S. are under a winter storm warning from an unusual blast of severe cold weather and snow across the South.

It is the first time in history that blizzard warnings are in effect along parts of the Gulf Coast from Texas into Louisiana.