The powerful nor’easter is causing coastal flooding and knocking out power to parts of the Northeast.

A powerful, slow-moving storm crept along the northeastern U.S. coast on Saturday, producing strong winds that knocked out power to thousands while whipping up large waves and heavy rain that created dangerous conditions in some places.

Tens of millions of people were in the Northeast Passage, which was expected to impact the mid-Atlantic region and New England through the weekend. About 100,000 customers in the region were without power Saturday.

Forecasts predicted no immediate respite. There will be “a lot of high winds, a lot of high tides and heavy rain possible over the next few days across the northeastern United States,” said Bob Oravec, chief forecaster for the National Weather Service in College Park, Maryland.

In the coastal neighborhood of Surf City, New Jersey, water flooded streets and inundated some homes.

Kenny Formica, owner of Surf City Marina on the Jersey Shore, was trying to stay busy Saturday as he sat at home watching the water rise inside his marina through surveillance cameras.

Water getting inside the building is rare, Formica said. The last time he remembers this happening was during Hurricane Sandy, which he estimates caused more than $4 million in damage to his business.

Before the storm, Formica said workers secured moorings, moved objects and equipment out of harm’s way and parked marina trucks and forklifts at the highest point on the property. Saturday morning, even these were almost surrounded by water.

Formica said he woke up Saturday to messages from customers reporting missing boats and jet skis. A customer sent him a video around 4 a.m. showing his 25-foot boat after it had blown off its lift.

“It’s like an 8,000-pound boat and, you know, a $150,000 boat that just disappeared,” Formica said.

In Edgewater, New Jersey, along the Hudson River, water poured into a large parking lot full of cars. Video posted on social media shows a car nearly submerged, with just its sunroof sticking out of the water, as people moved other vehicles away from the rising tides.

New Jersey communities prepare for major flooding

Videos verified by NBC News showed heavy tidal flooding Saturday at Shelter Marina in Beach Haven. Near Beach Haven Crest, ducks swam through the flooded streets. Video from a Spray Beach resident showed water covering a fire hydrant and entering garages.

Brian Kelly, mayor of the small New Jersey beach community of Sea Bright, said the borough is bracing for winds of up to 50 mph and flooding that could reach up to 6 feet on some streets. Authorities expect flooding to begin Saturday and worsen around midday.

“It’s going to be worse than average. We probably have one or two floods a year, sometimes more, sometimes less, but I think this one will be closer to an Irene-scale flood,” Kelly said, referring to the 2011 storm that caused significant flooding in the Northeast. “I hope I’m wrong, but that’s my intuition.”

Kelly hopes hundreds of residents living in low-lying areas will consider evacuating. He said the city would open its recreation center for evacuees.

Devastating winds threaten New England coast

Maximum wind gusts could approach 60 to 65 mph on Cape Cod, Martha’s Vineyard and Nantucket in Massachusetts on Saturday, compared to about 50 to 55 mph around Boston and 35 to 40 mph further inland, according to Matthew Belk, an NWS meteorologist in Norton, Massachusetts.

“The closer you are to the coast, the more likely you are to see impacts from the storm,” Belk said.

Belk said northeast winds are not unusual as fall approaches in New England, but a concern this early in the season is that leaves remain on the trees, creating more wind resistance. That could increase the risk of falling limbs, which could cause power outages and leave debris on roadways, he said.

Along the Atlantic coasts of New Jersey and Delaware, wind gusts could reach 60 mph, according to the NWS. In southeastern Connecticut and eastern Long Island, New York, gusts could be nearly as strong, potentially destroying tree branches and power lines.

Storm cancels flights, concerts and sporting events

The storm forced many people to change their plans. Hundreds of flights were canceled at Boston Logan International Airport, as were the vast majority of flights to popular Massachusetts tourist destinations Martha’s Vineyard and Nantucket.

The Boston Red Sox and Chicago Cubs – both preparing for the postseason during the final weekend of the Major League Baseball regular season – had to change the schedule of their three-game series. They played a doubleheader Friday in Boston to try to avoid the storm. MLB then rescheduled its final Sunday to take place in Florida, at the home of the Tampa Bay Rays.

Ed Sheeran has canceled his high-profile concerts Friday and Saturday at Gillette Stadium in Foxborough, Massachusetts.

Further south, a highway closure on North Carolina’s Hatteras Island scrambled Jayden Sink and Kimberly Laprad’s wedding plans Saturday.

The Virginia couple had arrived on the island before the storm, but most of their approximately 45 guests were stranded on the other side of the closure, the Island Free Press reported.

A local campground provided a new venue, cabins and a celebrant, and a DJ volunteered to provide the music. Organizers invited everyone on the island to come and celebrate with the couple on Saturday afternoon.

Authorities urge residents to exercise caution

Nor’Easters are not unusual as fall approaches in New England, but this one comes early in the season.

Officials in the east coast state urged people to exercise caution. Delaware Gov. Matt Meyer took to social media Saturday to implore people to keep an eye on the forecast.

New York State Gov. Kathy Hochul said coastal flooding posed the greatest threat, but the storm would also bring heavy rain, powerful winds and waves of up to 20 feet.

“The rain is underway and even though it’s only half an inch so far, mark my words: a lot more is coming,” the governor said early Saturday.