Torrential downpours have unleashed flash floods on the US Northeast that washed out roadways, overwhelmed rivers prompted 50 swift boat rescues, and killed a woman who was swept away in front of her fiance, officials said.

More than 13 million Americans were under flood watches and warnings from Eastern New York state to Boston and Western Maine to the northeast, the National Weather Service said in its forecast Monday, after storms that began over the weekend inundated rivers and streams.

Meanwhile, a Vermont reservoir threatened to overwhelm a dam protecting the state’s capital on Tuesday and exacerbate “catastrophic” flooding that has already shut roadways leading out of town and trapped some residents in their homes.

Private forecaster AccuWeather estimated damages and economic loss at $3 billion to $5bn, preliminarily, based on its own method of evaluation.

More than 1,000 flights to and from airports across the region, including New York’s LaGuardia and Boston’s Logan, were delayed or cancelled on Monday due to the rains.

Amtrak suspended passenger train service between the state capital Albany and New York City after flooding damaged tracks, as did the Metro-North commuter railroad which shares some of the same track.

New York and Vermont were the hardest-hit states.

Vermont officials were calling the flooding the worst since Hurricane Irene reached the state as a tropical storm in 2011.

“This is an all-hands-on-deck” event, Vermont Governor Phil Scott told a news conference.

Parts of Vermont had already received between seven and eight inches of rain, turning streets into raging rivers.

Some 50 isolated people were rescued by swift boat, said Mark Bosma, spokesperson for Vermont Emergency Management, on WCAX television. Officials expected rivers to flood overnight, posing risks to cities such as Montpelier, the state capital.

“We really want people to be hyper-vigilant and monitoring the weather and don’t wait too long to get higher ground,” Bosma said.

Swiftboat crews rescued about a dozen campers in Andover, said Jeanette Haight, the town’s clerk.

“A bridge washed out, and that was the only way in or out,” she said. “The call for help went out at 4am and they set up a swift-boat rescue. Everyone is safe this morning.”

In New York, more than eight inches of rain fell from Sunday to Monday in Stormville, a small town just over 50 miles northeast of New York City.

The weather claimed the life of an Orange County, New York, woman, swept away by floodwaters as she tried to leave her home with her dog on Sunday, officials said.

“Her fiance literally saw her swept away,” New York Governor Kathy Hochul told a press conference in the town of Highland Falls.

Much of the New York flooding was along the Hudson River north of New York City including the Orange County town of West Point, home to the Army’s US Military Academy.

Video and photos posted on social media showed washed-out roadways and raging floodwaters reaching houses on Sunday and early Monday morning.

“Oh my God. It’s up to my knees,” Melissa Roberts said in a video showing floodwaters rushing past her and several vehicles and up to homes in Orange County.

More rain forecast

Concerns over the Vermont dam have worsened as more rains threaten to cause additional flooding across Vermont, the northeastern corner of New York state and parts of Connecticut and Massachusetts, the National Weather Service said.

Light to moderate showers were in the forecast on Tuesday, before gradually diminishing throughout the day.

As much as another half an inch of rain was expected for the area, the service said, while rain showers and thunderstorms were in the forecast each day this week.

The Winooski is one of three major Vermont rivers that were cresting on Tuesday morning at or near record levels, said Weather Service forecaster Marlon Verasamy.

In Johnson, in central Vermont, the Lamoille River was at 21 feet, some five feet above its normal flood stage, he said.