A rare winter storm churned across the U.S. Gulf Coast on Tuesday, breaking snowfall records more than a century old in a southern region where flurries are unusual, as much of the United States remained in a dangerous deep freeze.

A rare frigid storm charged through Texas and the northern Gulf Coast on Tuesday, blanketing New Orleans and Houston with snow that closed highways, grounded nearly all flights and canceled school for more than a million students more accustomed to hurricane dismissals than snow days.