A heavy winter snow storm lashed the northeastern United States Thursday, subjecting New York to near blizzard-like conditions and forcing flight cancellations as schools and the United Nations closed.

Snow began falling overnight, following record high temperatures for February in New York on Wednesday, with as much as 14 inches (35 centimeters) accumulated in and around the city, and a bit more in other parts of the Northeast.

The FlightAware tracking website said that nearly 3,000 flights into or out of New York's three area airports, Boston and Philadelphia were cancelled.

In New York, America's most populous city, Mayor Bill de Blasio urged people to stay home and keep off the roads.

In Connecticut and Massachusetts, some areas experienced "thundersnow" -- the combination of snowfall and thunder, according to a meteorologist with the National Weather Service quoted by The New York Times.

The United Nations also announced that "due to inclement weather" its New York headquarters would be closed, while public schools also closed in the city, as well as in Boston and Philadelphia.

In New Jersey, Governor Chris Christie said state offices would be closed for all non-essential employees on Thursday.