Long Island finally got walloped.

Amid a relatively mild winter, a fast-moving snowstorm Thursday shuttered hundreds of schools, closed businesses, canceled flights, stranded vehicles, caused widespread rail delays and left behind a mess that highway crews were mobilizing to clean up in time for Friday morning’s rush hour.

The storm dumped up to 14 inches in some places, with Suffolk County taking the biggest hit. And while the system has left the region, it leaves chilly temperatures and blustery conditions that could freeze roadways.

Forecasters still have to determine whether Thursday’s storm ever morphed into an official blizzard, but areas of Long Island saw sustained winds of around 25 to 30 mph. Top gusts were in the 50s with a few — especially in Suffolk — reaching the 60s.

The swirling snow and near-whiteout conditions Thursday made for what Gov. Andrew M. Cuomo called “extremely dangerous” travel conditions. Still, the flurries ended by late afternoon, giving crews valuable hours into the night to plow roads, clear out parking lots and tow stranded cars.

The governor said the timing of the storm means “we should be in good shape” for the Friday morning’s commute.

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But several school districts — including Connetquot, Patchogue-Medford, Tuckahoe, Jericho, Bayport/Bluepoint and Southampton — said they would remain closed Friday, and many others were considering late starts or closings as well, officials said.

In Suffolk, which took the brunt of the storm, County Executive Steve Bellone declared a state of emergency at 11 a.m. as snow was accumulating rapidly — from 1 to 3 inches an hour. Travel conditions had begun to deteriorate around 7 a.m.

By Thursday evening, Bellone said county roads were passable but warned dropping temperatures and the tough time plow operators had reaching asphalt would make icy conditions likely for the morning commute.

“All county roads are passable, but there’s still much more work to be done,” he said. “There’s a strong likelihood of icy roads tomorrow.”

He urged residents to stay home if possible Friday morning or use caution if they have to go to work.

“If you do not need to go out, please stay at home,” Bellone said at a Commack news conference in front of a salt mound.

Suffolk Police Commissioner Timothy Sini said 911 call volume was lower Thursday than on a typical day, showing people had stayed off the roads. He said there were 90 motor vehicle accidents, with no fatalities or serious injuries as of 5:30 p.m.

Cuomo said at midday that there were “many, many ramps on the LIE where cars are stuck right now.” The state deployed a fleet of tow trucks to help the stranded motorists.

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The Long Island Expressway was “littered with disabled motorists” that had veered off the road into snowbanks, said Sgt. Rob Beccaris of Nassau police highway patrol.

Multiple accidents — including one involving a tractor trailer — occurred on the westbound Long Island Expressway. Two minor injuries were reported. A stretch of the westbound LIE was closed between exits 34 and 36 shortly before 10 a.m., and reopened about two hours later, officials said.

“If you don’t need to be on the roadway please don’t take to the roadway,” Nassau County Executive Edward Mangano said as the storm was kicking into gear. “It’s obviously treacherous conditions. With the visibility problem you can get yourself into much more serious trouble.”

Cuomo said among the factors that led him and his team to keep the roads on Long Island open was the state’s purchase of “dozens” more snowplows this year, which means more workers and equipment were out clearing the roads.

The at times-blinding snow kept most people at home, but some ventured out to head to work or experience the storm firsthand.

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The Long Beach boardwalk was a winter wonderland by noon, with several inches of snow piled up as more swirled and danced over the ocean’s crashing waves.

Local residents Jean and Ed Ruggiero, both 57, couldn’t resist making the short walk to the waterfront from their home with one of their daughters, even as gusting winds buffeted their every step.

“We always like to come down and see the beach in any kind of weather . . . definitely when something extra-special’s going on,” Jean Ruggiero said. “This fits that category.”

Public transportation withstood the weather. Major roads, airports, the Long Island Rail Road and New York City’s subway and bus system remained open.

But the storm played havoc with schedules. Delays at area airports were “extensive,” Cuomo said around midday.

By 10:30 a.m., the Port Authority reported 1,800 cancellations at its three area airports: Kennedy, LaGuardia and Newark Liberty.

Pamela Wach, 23, who was at JFK trying to get back to San Francisco after a trip to Israel, said her 9:30 a.m. flight had been delayed until 8 p.m. Thursday because of the weather.

“I’m so angry. I hate snow for exactly for this reason,” she said as she waited in the terminal. “There’s nothing I can do.”

Just after 9 a.m. Thursday, the railroad reported systemwide delays averaging 20 to 30 minutes. A total of 13 trains were canceled during the morning rush.

In the afternoon and evening it canceled 20 trains: three on the Port Jefferson/Huntington branch, seven on the Babylon branch, eight on the Port Washington branch and two on the Long Beach branch. Ridership was relatively light Thursday — about 40 percent of a typical weekday, the railroad said.

PSEG said a total of 37,168 customers had experienced an outage Thursday from the combination of high winds and heavy, wet snow. By 6:30 p.m. Thursday, more than 32,000 had been restored.

By 9:45 p.m., PSEG Long Island reported more than 99.8 percent of its customers have power.

The utility said 1,414 of its 1.1 million customers were without power at that time, with 1,393 customers out in Suffolk County.

As of 6:50 p.m., snowfall totals by trained spotters for the National Weather Service recorded, in Nassau, a range from 7 inches in Baldwin to 13 inches in Plainview; in Suffolk the range was 10 inches in Deer Park to 14.4 in Farmingville.

The intensity of the storm closed down many business that normally stay open in bad weather. One exception was Delicacies Gourmet in Roslyn.

Jim Zanfardino, the deli’s owner, said he has kept it open during every major storm for the past 27 years. He said residents have come to expect that.

“It’s kind of a sanctuary,” he said. “People trickle in here around noon.”

Gary Peters and his wife, Nancy Peters, both of Port Washington, said their drive to work in Roslyn was very “treacherous” and that there was hardly a car to be seen.

But snow was no deterrent for the demands of their day jobs as divorce attorneys at Peters & Peters in the Harbourview Shoppes in Roslyn, Gary Peters said.

“Neither snow nor inclement weather,” Peters said, “can obstruct liberating unhappy spouses.”