BOSTON (AP) — A blustering winter storm that dropped nearly 2 feet of snow just north of Boston, shut down major highways in New York and Pennsylvania and forced U.S. airlines to cancel thousands of flights nationwide menaced the Northeast on Friday with howling winds and frigid temperatures.

The brutal weather — which brought plummeting temperatures to some areas that forecasters predicted could see highs just above zero and wind chill readings of minus 10 degrees and colder by early Friday — dumped 21 inches of snow in Boxford, Mass., by late Thursday and 18 inches in parts of western New York near Rochester. Up to 7 inches fell in New York City by Friday morning.

The snowfall, frigid cold and stiff winds extended the holiday break for some students for a second day while posing the first test for New York City's new mayor and perhaps the last challenge for Boston's outgoing one.

U.S. airlines canceled more than 2,300 flights because of the snowfall and low visibility.

"It's been a tough road," traveler Heather Krochuk, of Toronto, Canada, said inside a Boston hotel Thursday night after her flight home out of Logan International Airport got canceled in what's turned into a 36-hour trip from Seattle, where she spent Christmas with her husband, Ron.

But, she said, "we have a place to sleep that isn't the airport."

Snow began falling overnight Wednesday in parts of New England and New York state, but the brunt of the storm began late Thursday. The National Weather Service issued a blizzard warning for Cape Cod, coastal areas north and south of Boston and part of Maine as well as New York's Long Island.

Forecasters warned that gusts of up to 30 miles per hour could bring wind chills to minus 25 degrees, cold enough to cause frostbite in about 30 minutes or less. The weather service said people should dress warmly to avoid hypothermia and cover all exposed skin.

Governors in New York and New Jersey declared states of emergency, urging residents to stay home. Massachusetts Gov. Deval Patrick said state offices that closed early Thursday would remain closed Friday. He said National Guard members and state police were on standby for any high tide flooding in vulnerable coastal areas, but no mandatory evacuations had been ordered.

New York Gov. Andrew Cuomo ordered three major highways in his state, stretching from Long Island to Albany, closed overnight. The Thruway between Albany and the Bronx reopened for passenger vehicles at 5 a.m. Friday and was scheduled to reopen to commercial vehicles at 8 a.m. The Long Island Expressway and Interstate 84 between the Pennsylvania and Connecticut borders were scheduled to reopen at 8 a.m. Southbound Interstate 95 closed in Philadelphia because of a jackknifed tractor-trailer.

As of late Thursday in Connecticut, about 3 inches of snow had fallen in Hartford County, and 3 inches were reported in East Hartford and Simsbury. Parts of New Hampshire had 5.5 inches, and areas of Rhode Island had more than 2.

Outreach teams looked to get homeless people off the frigid streets of New York City and Boston.

Staff members at the Pine Street Inn were keeping the Boston shelter open 24 hours and said they would turn no one away, even if it meant setting up extra cots in lobbies and other common areas.

The heavy weather began rolling in just a day after New York Mayor Bill de Blasio was sworn in to lead the nation's largest city and a few days before Boston Mayor Thomas Menino ends 20 years in office on Monday.

De Blasio, who as public advocate in 2010 criticized his predecessor Mayor Michael Bloomberg for his handling of a large snowstorm, dispatched hundreds of plows and salt spreaders on the streets as soon as the snow started falling Thursday night. Forecasters said that while only 5 inches of snow had fallen in Central Park by early Friday, up to 8 inches were still expected in the city.

"If you don't need to go out, please don't go out," de Blasio said at a news conference Thursday evening, urging residents to use mass transit. "Stay off the streets, stay out of your cars."

Across the region, state and local police were busy responding to accidents and reports of stranded vehicles.

Amtrak planned to run trains on all of its Northeast lines on Friday but operate on a modified schedule, spokeswoman Christina Leeds said. Metro-North Railroad, which runs trains between New York City and suburban Connecticut, Long Island and New York's Hudson Valley, was operating on a Saturday schedule, meaning about 60 percent of its typical weekday trains were running.

As the storm approached, a worker at a suburban Philadelphia salt storage facility was killed when a 100-foot-tall pile of road salt fell and crushed him. Falls Township police said the man was trapped while operating a backhoe. There was no word on what may have caused the accident.

Douglass Bibule shopped for rock salt and other supplies at a home improvement store in Watertown, N.Y.

"Well, there will be some shoveling that I will have to do and some sanding," he said. "I've got to go home and do some stretching exercises to make sure I don't hurt myself while doing that, and do a little shopping to make sure that we have all the supplies that we need. We need food because we have three older children at home."

The snowstorm worked its way east from the Midwest, where it dropped up to a foot of snow on Michigan and more than a foot in parts of Illinois, prompting the cancellation Thursday of hundreds of flights at both Chicago airports.

Nearly 17 inches of snow fell in some of Chicago's northern suburbs, and more than 12 inches of snow was recorded at Midway International Airport.

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Associated Press writers John Christoffersen in New Haven, Conn., Wilson Ring in Montpelier, Vt., Holly Ramer in Concord, N.H., Jim Fitzgerald and Jonathan Lemire in New York City, David Sharp in Portland, Maine, Bruce Shipkowski in Toms River, N.J., and Jackie Quinn in Washington, D.C., contributed to this report.