Above: A Von Karman vortex street downwind of the Canary Island chain in the eastern Atlantic Ocean off the coast of Africa on Feb. 27, 2015. Image credit: NASA Worldview. Editor's note ...

However, a deep freeze, thanks to the polar vortex dipping down from Siberia, is bringing an even harsher arctic blast to million Americans this week. Maps show what to expect as the cold front ...