Meteorologists warn that the coldest burst of Arctic air this season is coming to put an icy and prolonged exclamation point on America's winter of repeated polar vortex invasions starting this weekend.

The latest arctic blast will move into the northern Rockies and northern Plains Saturday and spread to the central and eastern U.S. through much of next week.

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,