It's like "bomb cyclone" or "firenado." It seems like the sort of phenomenon that would be responsible for the record-breaking blast of cold, snow and wintry conditions that reached all the way to the Gulf Coast this week.

A polar vortex dipping down from Siberia is bringing a cold front with frigid temperatures to millions Americans. See maps of the arctic blast.

An Arctic blast that began in the northern plains on Saturday spread bitter cold from the Rockies through the East Coast and as far south as Florida by Tuesday morning. A blizzard warning was in effect for southern Louisiana, the furthest south such a warning has ever been posted.

How the Polar Vortex Can Bring Arctic Blasts to the U.S. Vast weather patterns can carry blasts of frigid air far from the polar regions—here’s how it works

Most of the U.S. will enjoy milder temperatures on Thursday, but the warmup will be brief as a polar vortex will send temperatures tumbling below freezing for most of the nation starting this weekend.