BOSTON - The harshest week of winter thus far has begun, kicking off with several inches of snow in much of Massachusetts. Overnight, a widespread 4-8" of snow fell across most of southern New England.

Now that snow showers have wrapped up, we are left with arctic air. That will result in some bitter cold temperatures before improvements are made after the mid week.

A potent surge of Arctic air starts settling in Monday evening as a massive dip in the jet stream pulls in frigid air across the entire eastern half of the country. Temperatures are set to drop as low as 20 degrees below average through Thursday with the highs only reaching the teens and some lows even plunging below zero.