U.S. Representative Mike Lawler, who represents New York's Hudson Valley area north of New York City, posted several videos and photographs on Twitter showing rushing flood waters in Stony Point, a small town on the Hudson River about 40 miles north of Manhattan.
"Significant flooding in Stony Point - homes and cars - and many people evacuated," he wrote.
Similar flooding occurred in Pennsylvania. The Weather Channel showed video of flooded-out roads in Quakertown, located about 15 miles southeast of Allentown, where at least one stranded driver needed to be rescued by the fire department.
Bryan Jackson, a meteorologist with the National Weather Service's Weather Prediction Center, said a weather pattern more typical of cooler months had built over the Canadian province of Ontario and was interacting with the regular summer moisture.
Central Pennsylvania and southern New York bore the brunt of the rain on Sunday. The weather service predicted widespread and possibly catastrophic flash flooding for parts of New England on Monday.
The prediction center issued its first-ever high-risk warning, the highest level on a four-step scale, for the area surrounding Burlington, Vermont, on Monday, Jackson said.
"We expect considerable to locally catastrophic impacts," Jackson said.
The weather service urged people in some vulnerable areas to seek higher ground immediately.
On Sunday, the area near West Point, New York, home to the United States Military Academy, was under a flash flood emergency, having already received 9 inches (23 cm) of rain, according to radar estimates, Jackson said.
Blocked roads in New York's Orange County, which is home to West Point, prevented rescue teams from reaching isolated people, the New York Times reported, citing a county emergency management official.
(Reporting by Brendan O'Brien in Chicago and Daniel Trotta in Carlsbad, California; Editing by Leslie Adler)
