Hermine, a tropical storm that baffled forecasters and led to a voluntary evacuation of Fire Island, veered southeast and then north Sunday, brushing by Long Island even as it still threatens the area with potential flooding and gusty winds.

The storm that barreled up the Eastern Seaboard turned east by 9 p.m. Sunday, and after spinning back and forth, is slowly rumbling away from the region — packing much less of the punch it had days earlier, forecasters said.

“Definitely, the storm has tracked further east so the further away it is from us, the less impact there is,” said Jay Engle of the National Weather Service in Upton. “We have backed down to some degree in terms of the wind speed and the surf and coastal flooding.”

The service canceled the tropical storm warning for Nassau and New York City at 11:56 p.m. Sunday.

For many Long Islanders, Sunday was a beautiful day, in the high 70s with blue skies and light breezes.

Still, clouds and some showers will take over and overnight, there is concern about potential storm surges at high tide, rough surf and possible beach erosion as Hermine slowly passes by.

advertisement | advertise on newsday

Engle said coastal flooding could be a major concern overnight in some areas, adding that while earlier forecasts said between 2 and 4 feet of water could hit low-lying areas, a revised prediction held that between 1 and 3 feet would result.

By 7 p.m. the storm showed signs of moving on a “slow north-northwest track” early Monday into Tuesday, the National Hurricane Center said Sunday night.

The center said Sunday night the closest approach of the storm would be a little more than 100 miles south of Montauk Point and 200 miles southeast of New York City.

The center continued to warn that Long Island could still experience strong winds and coastal flooding before Hermine checks out.

The center, in its 7 p.m. briefing, said, “Significant storm surge with moderate to major coastal flooding is possible around the times of high tide Monday for low-lying communities across Long Island.”

Earlier in the day, the center had said a storm surge watch remained in effect for only coastal Long Island, and officials had canceled the watch for all other areas, including New York City and the shore of New Jersey.

No heavy rainfall was expected from the storm on Long Island, the center said.

Earlier, forecasters tracking Hermine said the storm was also churning up dangerously large waves and potentially deadly riptides.

State parks on Long Island closed their beaches to swimmers. Suffolk County beaches also were closed to swimming Sunday.

Surveying the beach line in his SUV late Sunday night, Robert Moses State Park manager Tim Byrne pointed out where the ocean had eaten away a 60 to 70 foot stretch of sand.

advertisement | advertise on newsday

He pointed to where the edges of the sand dropped two feet down. “It’s getting chewed up a bit,” he said. “There’s a little cliff.”

Earlier at the closed beaches, park officials blocked four-wheel drive vehicles from parking and driving on the sand, and access will be evaluated Monday after the morning high tide, said George Gorman, state parks’ Long Island regional director.

“As a precaution, we closed them down so that no one would go out there tonight and wind up in trouble, under water or flooded out or being blocked access because the road’s flooded,” Gorman said.

Suffolk’s Emergency Operations Center will open at 5 a.m. Monday with representatives from state, county and town agencies, utilities and the Long Island Rail Road in the basement of a county building in Yaphank.

Earlier, residents and visitors to Fire Island had been asked to evacuate by Suffolk leaders Saturday and Sunday.

advertisement | advertise on newsday

Dozens began leaving Fire Island’s beaches Sunday, arriving in Bay Shore by ferry with luggage, coolers and other summer gear in tow.

The evacuees left the boat and made their way through a crowded dock and parking lot, their end-of-summer trips cut short, and described scenes of an isolated town with empty beaches and rough waves.

“We’re bummed out, but we had a great week,” said Cheryl Goveia, 56, of Islip, who was leaving with her family. They had rented a beachfront home and were scheduled to return from a nine-day trip on Monday.

She said she heeded the call of emergency officials on the beaches, where sirens blared to warn people of the evacuation all weekend.

Goveia chose to leave Sunday morning rather than in the afternoon to avoid a “mass exodus,” she said.

Michael Solomon, 52, of Short Hills, New Jersey, and his family left their home in the Summer Club community in Ocean Beach. They had spent the weekend securing their outdoor furniture or bringing it inside.

“Packing in for the summer,” Solomon said. “It’s always better to be safe than sorry. Usually we play it by ear and stay as long as possible. This week we just couldn’t.”

About two dozen passengers left for Fire Island about 11:30 a.m. on a ferry. Many said the evacuation would give their children extra time to prepare for the start of a new school year.

PSEG Long Island officials said Sunday that they would continue to monitor the track and potential impact Hermine will have on its service territory through the week and that the utility is ready to respond to possible power outages.

“Receiving support from off-Island utilities and contractors that will work alongside our own highly trained line personnel will allow us to promptly and safely restore power to our customers,” said John O’Connell, vice president of transmission and distribution for PSEG Long Island. “All crews will work 16-hour shifts once the restoration efforts begin.”

Aaron Donovan, spokesman for the Long Island Rail Road, said the agency was “carefully monitoring the storm and pre-positioning equipment and personnel to be able to deal with any effects of downed trees or coastal flooding.”

Workers for PSEG Long Island were trimming trees in advance of the storm, and shoring up low-lying substations to keep water out, according to spokesman Jeffrey Weir.