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ac dnt gray polar vortex return_00010727.jpg
ac dnt gray polar vortex return_00010727.jpg

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    What is the polar vortex?

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What is the polar vortex?

Brace yourselves -- the polar vortex is going to send more cold air. But how does it do it? CNN's Jennifer Gray explains.

What is the polar vortex?

Brace yourselves -- the polar vortex is going to send more cold air. But how does it do it? CNN's Jennifer Gray explains.