More than 70,000 customers across the U.S. Northeast were without electricity Saturday as a powerful nor’easter battered the region, bringing strong winds, heavy rain, and the threat of significant flooding.

The National Weather Service warned that the storm could produce major coastal flooding along the Mid-Atlantic through multiple high-tide cycles, with New Jersey and Delaware among the areas facing the greatest risks. Officials urged residents in low-lying coastal areas to prepare for roads to become submerged and water to reach homes and businesses.

Flooding was already affecting coastal communities in New Jersey. Streets in Surf City were inundated with seawater, with flooding reaching some homes, while roads in nearby Manasquan were also taking on water. Manasquan Mayor Mike Mangan said he expected significant amounts of water to remain in the streets for an extended period.

Some low-lying areas had already issued voluntary evacuation notices. In Sea Bright, Mayor Brian Kelly said officials were preparing for winds of up to 50 mph and flooding that could reach 6 feet on some streets. The community planned to open its recreation center for residents who choose to evacuate.

The storm was also expected to bring dangerous winds farther north. Gusts could reach 60 to 65 mph across Cape Cod, Martha’s Vineyard and Nantucket, while Boston could see gusts around 50 to 55 mph. Parts of New Jersey, Delaware, southeastern Connecticut and eastern Long Island could also experience gusts near 60 mph.

Meteorologists warned that the timing of the storm could increase the risk of power outages because leaves remain on trees across New England. Strong winds pushing against the foliage could bring down branches and trees, potentially damaging power lines and blocking roads.

The storm was already disrupting travel throughout the Northeast. Dozens of flights were canceled at airports in Boston, Nantucket and Martha’s Vineyard, while FlightAware reported 39 cancellations at Boston Logan International Airport between 6 a.m. and 10 a.m. Saturday. Another 12 flights at Logan were delayed.

Ferry service was also disrupted between Cape Cod and the islands of Nantucket and Martha’s Vineyard, with cancellations caused by strong winds and rough waters. Ferry service to Block Island in Rhode Island was likewise canceled, with additional disruptions expected Saturday.

The weather forced changes to major events as well. The Boston Red Sox moved their Sunday afternoon game against the Chicago Cubs to Friday as part of a split doubleheader, while singer Ed Sheeran canceled his Friday and Saturday performances at Gillette Stadium in Foxborough, Massachusetts.

Residents in coastal communities were preparing for the possibility of prolonged power outages and flooding. Some secured boats and other property, while others brought out generators and stocked up on activities and supplies to remain indoors through the weekend.