The polar vortex hit its peak across much of America on Wednesday, with an icy grip that made Arctic Greenland seem like a toasty vacation spot in comparison. Even Mars has been warmer than North Dakota this week.

An Arctic blast tied in part to the polar vortex is driving record frigid air south from the Northern Plains toward the Gulf Coast Wednesday in a cold snap that will last the entire week. Threat level: This event is setting daily record cold temperatures and is forecast to bring for the coldest temperatures on record for this late in the season.

The polar vortex is not synonymous with cold snaps, but when it slides toward the United States, the polar jet stream can mirror the distortion and introduce Arctic air. While this distortion is often caused by weakening of the polar vortex, that’s not the case this time.