Rising Arctic temperatures and melting sea ice could be causing cold air to flow into the Northern Hemisphere. But not all scientists agree.

The North Pole is surrounded by a massive circular upper-air weather phenomenon in the Arctic called the polar vortex. It is a typical pattern that tends to contain the coldest weather close to the North Pole and is more pronounced in the winter.

A winter storm descending on the US is expected to deliver heavy snow and ice to more than 150 million people across roughly two dozen states. Forecasts predict the storm will plunge Texas into a deep freeze before moving eastward and hitting major Northeast cities such as New York City and Boston.

Meteorologists warn that a stretched polar vortex could bring severe winter weather to much of the United States.

As the U.S. prepares to take on another bout of cold weather, the term "polar vortex" is getting thrown around. But what is it?

Despite being notorious for bringing brutal cold and dangerous wind chills, the polar vortex has a surprising upside. Discover how it can lead to clearer skies, fewer storms, and ideal conditions for winter activities.

The meteorologists said the polar vortex system is set up due north of Michigan over Canada's Hudson Bay. It's at least partly responsible for the frigid temperatures around the region that contributed this week to a 100-vehicle pileup in southwest Michigan and led the city of Detroit to declare a cold weather health emergency.

After this weekend's snow storm moves out, cold Arctic air will move in.

Tens of millions of people are in the path of a major winter storm. Federal cuts threaten efforts to understand the causes of such weather.

It exists all the time, but it usually gets stronger in winter. When the jet stream (a river of wind) bends and dips south, the edge of the polar vortex can wobble or stretch. That can let Arctic air slide into the United States and Canada and bring a short spell of extreme cold.

The big winter (and popular) topic is dusted off very early this season as frigid air plunges south next weekend. But what is the Polar Vortex, exactly?