Polar vortex: cold snap threatens millions of people

Several waves of frigid, arctic air threatens millions of people. They are expected to sweep across the eastern half of the country in the coming weeks. The first blast of severe cold will affect the northern Plains and Midwest this Thursday and is forecast to reach the Northeast later this week.

Similarly, forecasters note that with increasing cold temperatures, snowfall is likely in several areas.

"Below freezing temperatures may occur as far south as the Gulf Coast and much of the Florida Peninsula. Impacts to highly sensitive citrus crops are possible," the National Weather Service's Climate Prediction Center explained.

In that regard, Axios explained that "the coldest air of the season so far and dangerous wind chills are expected across much of the Southeast from Jan. 7-13."

According to the National Weather Service, a polar vortex is a large area of low pressure and cold air surrounding the Earth's poles. It always exists near the polar areas but weakens in the summer and intensifies in the winter. The term "vortex" refers to the counterclockwise rotation that allows cold air to remain near the poles.