What exactly is the polar vortex?

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.
Read more: https://theconversation.com/what-exactly-is-the-polar-vortex-153958?source=Snapzu