The coldest burst of Arctic air this season is coming to put an icy exclamation point on America's winter of repeated polar vortex invasions, meteorologists warn. And it will stay frozen there all next week.

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.

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, with the cold moderating some as it barrels east through late week.