Originally Published: 10 JUL 23 01:54 ET

Updated: 10 JUL 23 15:23 ET

By Lauren Mascarenhas, Nouran Salahieh and Paradise Afshar, CNN

(CNN) — Intense rain and flash flooding that left at least one dead in southeastern New York continued to pelt the Northeast on Monday, forcing residents from their homes and prompting road closures and water rescues.

Over 9 million people are under flood alerts across the Northeast on Monday, including parts of New York, Vermont, Massachusetts and Maine – as well as across the country in Washington and Alaska. Flash flood emergencies and landslides are expected, with heavy rainfall expected throughout the day.

The National Weather Service issued a flash flood emergency warning for central Vermont on Monday, where 19 people have been rescued by boat and 25 others have been evacuated, Vermont’s Urban Search and Rescue team coordinator Mike Cannon told reporters.

Two areas in the state that have been severely impacted, Weston and South Londonderry, are currently inaccessible due to flooding, and search and rescue teams are working to regain access and perform welfare checks, Cannon said.

Gov. Phil Scott declared a state of emergency Sunday as the weather service warned flash flooding could become “extremely dangerous.”

“My friends, this is the new normal,” New York Gov. Kathy Hochul said, addressing the havoc that the storm is wreaking in the state, where more than 8 inches of rain fell within a 24 hour period in some locations in the state. Hochul issued states of emergency for both Orange and Ontario counties.

A 35-year-old woman died Sunday, swept away by floodwater as she tried to evacuate her Orange County home. The flooding has caused “easily tens of millions of dollars in damage,” county Executive Steve Neuhaus said Monday.

Many residents who tried to drive out of the area Sunday were trapped, Neuhaus said. “We saw many cars that tried to go for it through the water, didn’t make it, and got stuck,” he said, adding that he saw “active duty Army soldiers up to their bellies … we were walking to cars to make sure people got out.”

In western New York’s Ontario County, door-to-door checks were conducted at about 120 homes, which prompted the voluntary evacuation of more than a dozen individuals and five pets, according to Hochul. Officials in the area have set up a temporary shelter.

Hochul said FEMA and White House officials have offered to assist with the response.

“While the storm has already passed through the southern part of New York, conditions remain dangerous in further north where there are ongoing extreme weather conditions. I urge all New Yorkers to remain vigilant, monitor local forecasts and have an evacuation plan ready if you’re in a danger zone,” Hochul said.

Once-in-a-millennium rainfall

Rainfall in West Point, New York, totaled more than 7.5 inches in six hours Sunday afternoon, according to preliminary data from the National Oceanic and Atmospheric Administration. That’s a 1-in-1,000 year rainfall event for the area, according to a CNN analysis of NOAA’s historical rainfall frequency data.

A once-in-a-millennium rainfall event is one that is so intense, the chances of it happening in any given year is just 0.1%.

Reading, Pennsylvania, received 5.35 inches of rain Sunday, shattering its old daily rainfall record of 3.47 inches, set in 1952.

Areas across New England could see 3 to 5 inches of rain Monday, which could bring rainfall totals for this storm up to 12 inches.

A moderate risk, Level 3 of 4, of excessive rainfall is in place in New England through early Tuesday. Rainfall totals across the area are expected to range from 3 to 5 inches.

Intense rainfall rates are expected to continue in Vermont and northeastern New York throughout Monday, according to the weather service. New York could see 1 to 2 inches of rain per hour, the NWS warned.

Vermont is facing a rare risk of potentially catastrophic rainfall, which could push isolated storm totals toward 12 inches when combined with the rainfall that already fell across the area over the weekend.

“The threat is exacerbated by the fact that the ground is already saturated from recent rainfall events,” the weather service said.

Numerous rivers have been rising as a result of heavy rainfall and flash flooding around the state, which will likely lead to additional flooded locations over the next 24 hours.

The Winooski River at Montpelier has risen more than 8 feet in 10 hours and is currently nearing 14 feet in elevation. The river is expected to rise another 5 or more feet by Tuesday morning, according to projections from NWS’ Northeast River Forecast Center. This would put it just above the crest experienced during flooding associated with Hurricane Irene in 2011 and will likely result in flood waters covering streets in downtown Montpelier.

The White River in West Hartford has similarly seen a rise of 10 feet in 10 hours since Monday morning, and is expected to crest above 20 feet for the first time since Irene in 2011.

Nearly a dozen different locations across Vermont from the Connecticut River in the south to the Missisquoi River in the north will experience moderate or major flooding before river levels begin dropping Tuesday.

In a Monday Facebook post, Scott said the state was enacting an “all-hands-on-deck” response to the extreme flooding. “We have not seen rainfall like this since Irene, and in some places, it will surpass even that,” the governor said.

In New York, Gov. Hochul urged residents to stay home. “Flash flood warnings mean travel is extremely dangerous. Please, don’t take any chances,” Hochul said. “Stay home, stay off the roads, and stay safe.”

New York City’s Emergency Management Department cautioned residents living in basement apartments “to be prepared to move to higher ground.” Heavy rains continuing through Monday morning “may cause rapid flooding to basements with little to no notice and can be life threatening,” an alert from the agency sent Sunday afternoon reads.

When torrential rain from Hurricane Ida caused flooding in New York City in 2021, most of the homes where residents were found dead were illegally converted basement or cellar apartments, city officials said.

“Do not underestimate the power of fast-moving water,” Hochul said. “Two feet of fast-moving flood water will float your car, and water moving at two miles per hour can sweep cars off a road or bridge.”

And in Massachusetts, the towns of Williamsburg, Clarksburg, Deerfield and Becket, as well as the city of North Adams, have all declared emergencies, a spokesperson for the Massachusetts Emergency Management Agency told CNN. Residents should expect rivers, creeks and streams to rise gradually through Tuesday.

Trapped drivers had to swim out of their cars

Two dozen residents were evacuated and two town employees were rescued from flooding Monday in Ludlow, Vermont, where routes in and out of the city were blocked, Ludlow Emergency Management Director Angela Kissell told CNN. “There’s currently debris and water blocking the main roads. We’re an island right now,” Kissell said.

Ten people were rescued from a campground in Andover, Vermont when a bridge at Horseshoe Acres Campground was washed out, leaving campers trapped, said Jeannette Haight, the town clerk and treasurer.

In New York’s Orange County, people were trapped by floodwaters at the US Military Academy at West Point and had to swim out of their cars to get to safety, a West Point Military Police spokesperson told CNN on Sunday.

Many residents who tried to drive out of the area were trapped, Neuhaus, the county executive, said. “We saw many cars that tried to go for it through the water, didn’t make it, and got stuck,” he said, adding that he saw “active duty Army soldiers up to their bellies … we were walking to cars to make sure people got out.”

In the same county, the town of Cornwall issued a “No travel Advisory” Sunday after storms flooded multiple roads, triggered mudslides and forced rescues from stranded cars. In nearby Rockland County, state police also reported “numerous motorists stranded” due to flooding in the area.

Firefighters in Canandaigua in Ontario County, New York, received over 150 water related calls and performed dozens of rescues, Canandaigua Fire officials tweeted Sunday, sharing a photo of people kayaking through deluged streets.

Eastern Pennsylvania also saw “significant” flash flooding Sunday afternoon, according to the weather service. The Fleetwood Police Department shared images of deluged roadways in Berks County and urged residents to avoid all travel, adding that crews were out responding to rescues and flooded basements Sunday.