The polar vortex appears to be on the move.
That's because stratospheric warming is occurring at high altitudes above the North Pole, resulting in a spike in temperatures.
That, in turn, could result in bitter cold air pushing southward into the United States within a couple of weeks, though where exactly that Arctic air will swoop down - and for how long - remains uncertain.
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How the polar vortex works.(CNN)
The polar vortex is simply a low pressure system that swirls cold air around the polar regions of the globe.
But the system can sometimes move off the North Pole.