What Is a Polar Vortex? Arctic Weather Pattern Set to Blast Over a Dozen States With Season's Coldest Temperatures

Hang on to your coats and scarves: While the first part of this week brought a brief reprieve from the brutally cold weather the U.S. has been experiencing since January, frigid temperatures are about to make a comeback. 

According to Accuweather, a cold front will come through the Great Lakes and Ohio Valley regions as well as the Northeast later on this week, “bringing another round of plunging temperatures and snow.” Fox Weather notes that some areas of the Northeast will experience wind chills that make it feel like -25°F in some areas.

This weather comes courtesy of what’s known as a Sudden Stratospheric Warming, in which temperatures in the stratosphere over the Arctic rocket upward, disrupting the polar vortex, perUSA Today. 

“Polar vortex” is a term bandied about often in the wintertime—but what exactly is it?

The Polar Vortex, Explained

The polar vortex is a low-pressure area of cold winds, positioned 10 to 30 miles above the North Pole, that typically blows around the pole in a west-to-east direction (hence the term “vortex”). It’s kept in place by the polar jet stream, which is located between 5 and 9 miles above the surface. 

In the winter, according to the National Environmental Satellite, Data, and Information Service (NESDIS) at the National Oceanic and Atmospheric Administration (NOAA), “the polar vortex at the North Pole expands, sending cold air southward.” This not-uncommon occurrence brings colder temperatures to the U.S. (as well as to areas of Europe and Asia).

But when the polar vortex is disrupted by an event like a Sudden Stratospheric Warming, it weakens—sometimes, it’s even pushed from the pole, splits, or, in extreme cases, reverses direction. As NESDIS explains, “Without that strong low-pressure system, the jet stream does not have enough force to maintain its usual path. It becomes wavy and rambling. When high-pressure systems get in its way, a collection of cold air pushes south, along with the rest of the polar vortex system.” States as far south as Florida can feel those colder temperatures. According to NESDIS, this severe weakening of the polar vortex happens about every other year. You can see a video of January’s polar vortex, as snapped by NASA satellites, below.

https://www.youtube.com/shorts/d0znFEjkjJc

As the National Weather Service points out, polar vortexes are not a new phenomenon, even if the term itself has only become more widely used in the last couple of decades: “The term … [is] bringing attention to a weather feature that has always been present.” 

How to Prepare for Very Cold Weather

According to AccuWeather Senior Meteorologist Alex Sosnowski, the air coming down from the polar vortex this weekend could “supply the actual lowest temperatures of the season” in the Northeast, and per Fox Weather, things won’t start to warm up until mid-month—so it’s important to make sure you’re ready.

Related: Winter Weather Warnings Announced for 8 States as 50 mph Winds, More Snow Approach

The National Weather Service recommends preparing for cold temperatures by filling up your car’s gas tank and putting together a cold weather car survival kit. They also suggest avoiding going outside in the early morning hours, when it’s coldest, dressing for the outdoors even if you don’t plan to go out (they have a handy infographic for that). You should also take steps to prevent your pipes from freezing. 

But it might be best to stay inside as much as possible—as AccuWeather meteorologist Peyton Simmers notes, “People should limit time outdoors as hypothermia and frostbite can set in rather quickly, especially on areas of exposed skin.”