What is a polar vortex? And why isn't this cold blast one?

Brutally cold temperatures are heading to the Midwest and Northeast this week -- but don't mistake this for a polar vortex taking aim on the United States.

What we call the polar vortex -- a spin in the atmosphere -- can't actually be felt in the U.S. or anywhere on Earth.

The polar vortex lives in the upper atmosphere, including the upper troposphere and the stratosphere, and is located near the North Pole in the arctic.

When the polar vortex is strong, it locks the cold air in the arctic.

It's when the polar vortex gets weaker, or breaks up, that it unleashes cold air to the south.

So the next time you hear someone talking about the entire polar vortex heading our way, just pull on your hat and gloves and remember that the polar vortex itself isn't moving across the U.S. -- and focus on preparations for the cold.