Frigid air that normally stays trapped in the Arctic has escaped, plunging deep into the United States for an extended visit that is expected to provoke teeth-chattering but not be record-shattering.

It's another day of brutally cold temperatures and dangerous wind chills across much of the United States.

It’s another day of brutally cold temperatures and dangerous wind chills across much of the United States.

Forecasters are warning of treacherous holiday travel and life-threatening cold for big parts of the nation, an arctic air mass blows into the already-frigid southern United States.