Forecasters have said parts of the U.S. can expect frigid temperatures in December. A first round has arrived, and more cold air could be coming.

Thanks to the polar vortex, the first half of December will bring multiple waves of Arctic air to the U.S. Here's what to expect in Tennessee.

Polar vortex systems will bring dangerously cold weather to much of the U.S. this month. Learn how to stay safe, and which health conditions put you at higher risk.