Even though the calendar doesn't officially mark the arrival of winter, a lot of the country is already experiencing cold temperatures.

Most of the north and eastern U.S. will experience below-normal temperatures throughout the next week, with many areas already under freeze warnings and watches, as many vehicles head home from their Thanksgiving vacations. A blast of icy Arctic air was the blame.

Meteorological winter begins on December 1 and is initiated by this weather occurrence. Naturally, the winter solstice on December 21 marks the start of astronomical winter.