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What the heck is that word I keep hearing?

A polar vortex (kyokūzu/極渦) is a persistent, large-scale cyclone located near either of a planet’s geographical poles. The extreme arctic blasts that wreaked havoc across the United States last week were caused by a counterclockwise-rotating pool of cold, dense air. The frigid air, piled up at the North Pole, was pushed south, making it as far as the Gulf Coast.