By Scott Malone and Joseph Ax

BOSTON/NEW YORK (Reuters) – The heaviest storm the northeastern United States has seen this year was bearing down on the region on Thursday, forcing schools in major cities to cancel classes and airlines to ground thousands of flights.

Forecasters predicted the storm could bring more than a foot (30 cm) of snow and wind gusts up to 50 miles per hour (80 kph) from Pennsylvania through Maine.

New York City schools, the largest public school system in the United States, with more than 1 million students, canceled classes on Thursday. So did districts in Boston and Philadelphia.

More than 2,700 flights in and out of the region were also canceled, according to Flightaware.com, as airlines told passengers to check the status of their flights before heading to the airport.

Blizzard warnings were in effect for the eastern end of New York’s Long Island, Cape Cod, Massachusetts and the island of Nantucket.

“Early start. Getting Ready to go out and battle the snow storm so that I can do what I need to do,” tweeted IT professional Andy Quayle in New York City.

With the storm expected to dump as much as to three inches (8 cm) per hour and start before the morning rush hour and last into the evening, mayors of major cities, including New York and Boston, warned residents to stay off the roads.

“Visibilities will become poor with whiteout conditions at times. Those venturing outdoors may become lost or disoriented. So persons in the warning area are strongly advised to stay indoors,” the National Weather Service said in an advisory.

Temperatures were expected to fall to single-digit Fahrenheit levels (below -12.8°C) overnight in the Boston area.

The forecast comes a day after much of the northeast saw spring-like weather, with temperatures of 50 to 60 degrees Fahrenheit (10 to 16°C).

“I’ve never seen anything like this in my life, you know, what feels like a summer day, almost, now, and then tomorrow a blizzard,” New York Mayor Bill de Blasio told WCBS-AM radio. “But it’s going to be a blizzard and New Yorkers should get ready.”

While temperatures had been mild for much of the region on Wednesday, New England highways were clogged with scores of car crashes that morning after an early rain storm coated roads in ice. At least one person was killed in Massachusetts when he was struck by a car as he tried to help another motorist..

“We want people to stay indoors as much as possible,” Boston Mayor Marty Walsh told reporters on Wednesday.

(Reporting by Scott Malone, editing by Larry King)