What Exactly Is the Polar Vortex?

City of Richardson worker Kaleb Love breaks ice on a frozen fountain in Richardson, Texas, on Feb. 16, 2021. LM Otero/AP Photo

At the start of February 2021, a major snowstorm hit the northeast United States, with some areas receiving well over two feet of snow. Just a few weeks earlier, Spain experienced a historic and deadly snowstorm and dangerously low temperatures. Northern Siberia is no stranger to cold, but in mid-January 2021, some Siberian cities reported temperatures below minus 70 F (minus 56 C). Media headlines hint that the polar vortex has arrived, as if it were some sort of ice tornado that wreaks wintry havoc wherever it strikes.

As atmospheric scientists, we cringe when the term polar vortex is used to loosely refer to blasts of cold weather. The actual polar vortex can’t put snow in your backyard, but changes in the polar vortex can load the dice for wintry weather – and this year, the dice rolled Yahtzee.

The Winds of Winter

The polar vortex is an enormous, three-dimensional ring of winds that surrounds the North and South poles during each hemisphere’s winter. These winds are located about 10 to 30 miles (16 to 50 kilometers) above Earth’s surface, in the layer of the atmosphere known as the stratosphere. They blow from west to east with sustained speeds easily exceeding 100 mph (160 kph). In the darkness of the winter polar night, temperatures within the polar vortex can easily get lower than minus 110 F (minus 79 C).