What is the polar vortex (and why is it happening again)?

All the horrors of winter in one small twitch of the jet stream

cold pug in a blanket
Nope nope nopePixabay

It’s the chill that runs down your spine in the dark when you suddenly realize you aren’t alone. It’s the fog of a Dementor’s breath on the windows of the train. It's everything that embodies the chill devastation that has gripped our hearts in 2016.

Yes, my friends. It-that-shall-not-be-named has returned to stalk the streets of America, from the midwest to the northeast.

It's the polar vortex.

Scary, right? But the polar vortex is actually just an area of low pressure near the poles. Filled with chilly Arctic air, the Northern polar vortex is always there, but expands in the winter. Sometimes that cold air drifts down past the Canadian border and into the United States, where everyone immediately panics because suddenly it is very very cold outside and that is NOT OK.

But according to the National Weather Service, the movement of the polar vortex is totally normal—even if it throws an icy wrench in your winter plans. Though it occurred most recently in 2014 (and many of us are still recovering from the experience), similar bursts of cold have occurred in 1989,1985, and 1977.

Here's how it works:

Polar Vortex

Polar Vortex

A helpful diagram of our latest apocalypse.National Weather Service

As the aforementioned mass of cold air rotates slowly around the polar region, it isn’t completely isolated from the surrounding air in the lower latitudes. If an area of warm air appears near the steady polar vortex, high in the atmosphere, this can sometimes disturb the system and push a lobe of cold air further south than it would normally go, with the jet stream moving south right along with it.

That pocket of cold air is responsible for the cold temperatures—20-30 degrees below normal, in fact—that forecasters expect to hit the midwest and northeastern regions of the country this week. An even harsher encore is expected over the weekend. In some places those bitter temperatures will also be accompanied by snow, so pay attention to the forecast and get your shovels (and cocoa) ready.

The best way to get through it? Brace yourself. Even if they come from a weather phenomenon with a hyped-up name, temperatures below zero are nothing to sneer at. Bundle up and minimize your time outside. Better yet, just Netflix-and-freeze into a solid block of ice. It won’t be too hard in these temperatures.