The National Weather Service says the weather system causing gusting winds and frigid temperatures dumped 21 inches of snow just north of Boston and up to 18 inches in parts of  New York state late Thursday.

U.S. airlines have canceled more than 2,300 flights nationwide and some school systems in New England and New York extended Christmas break.

Travelers at San Diego's Lindbergh Field are contending with at least nine cancellations and long lines so far on Friday.

Forecasters predict temperatures will plummet, with some areas seeing highs just above zero and wind chill readings below zero.