BOSTON -- A strong winter storm pounding the Northeast with stiff winds and punishing cold has dumped nearly 2 feet of snow in parts of Massachusetts.

The National Weather Service says 21 inches of snow has fallen in Boxford, just north of Boston. It says parts of upstate New York have 18 inches.

The brutal weather has extended Christmas break for some students while posing the first test for New York's new mayor and perhaps the last challenge for Boston's outgoing one.

Some schools in New England and New York closed well ahead of the Thursday snowfall. Cities have mobilized plows and salt spreaders. Some major highways have been ordered shut down overnight. Efforts are underway to get homeless people into the warmth and safety of shelters.

U.S. airlines have cancelled more than 2,300 flights nationwide.