A rare winter storm charging through Texas and the northern Gulf Coast on Tuesday has closed highways and airports and prompted the first blizzard warning for southeast Texas and southwest Louisiana.

So many of you have never seen an event like this,” Louisiana’s state climatologist warned, with New Orleans facing possibly the most snow it has ever seen.

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