Polar vortex freezes US Midwest with snow, dangerously cold air

The Midwest was the hardest-hit region, as temperatures plunged below zero Fahrenheit (minus 18 degrees Celsius). By nightfall the mercury was hovering at 0F in Chicago, 7F (minus 14C) in Detroit and minus 21f (minus 29C) in Minneapolis. The brutal blast known as the polar vortex is a stream of cold air that spins around the stratosphere over the North Pole.

from US News Headlines, Latest USA News, America Breaking News - Times of India http://bit.ly/2UsEDYR