In case you needed another reason to hibernate in the coming weeks, the polar vortex is returning and bringing with it the coldest temperatures of the year.

The polar vortex, a low-pressure mass of cold air over the Arctic, has been known to sometimes shift outside of its Northern habitat, bringing colder temperatures to the Northern regions. Last month, the vortex actually split, which sent freezing temperatures toward the Eastern part of the United States. Northeastern and Midwestern states may recall the chilling cold front that swept thru both regions earlier this month, and many should prepare for an even harsher cold that's expected at the end of January. 

In about a week, temperatures are expected to drop 20 to 40 degrees below Fahrenheit. The temperature in New York City is expected to be in the teens, with other cities like Cleveland and Chicago reaching 0-degree highs. In the Midwest, where the winter climate is notoriously brutal, areas near Duluth, Minnesota are expected to receive -25-degree temperatures. 

"From this Thursday night through late next week, it will be a very cold stretch," said AccuWeather's Lead Long-Range Meteorologist Paul Pastelok. "The end of January will bring the coldest air of the season for the Midwest and rival the Arctic blast from earlier this week as the coldest in the Northeast." 

One of the major causes of the vortex's split has to do with a failure to maintain equilibrium. When the vortex grows weak, lobes of the vortex can potentially travel southward towards the U.S. and Europe. Dramatic warming is one of the principal causes of a weakening vortex, termed sudden stratospheric warming

If you've been saving up those vacation days at work, this may be the time to use them.