A week-long, polar vortex-related Arctic outbreak rivaling any seen so far this winter is slated to bring frigid conditions to much of the U.S. east of the Rockies next week. Threat level: The Arctic air is likely to send temperatures plunging to at least 30 degrees below average for mid-February across the Midwest and Plains states,

After a winter storm this weekend, the polar vortex will return, bringing subzero temperatures to around 80 million people from Montana to Maine and potentially as far south as northern Texas.

The vortex is essentially an area of low pressure in the upper layers of the atmosphere over the polar region up north. This vortex consists of powerful westerly winds in the stratosphere, about 10 to 30 miles above the North Pole, according to Climate.gov.