The remnants of Tropical Storm Lee poured water on top of the already soaked Northeast on Thursday, closing hundreds of roads and forcing evacuation orders for more than 100,000 people from the Susquehanna River's worst flooding in nearly 40 years.

Most of the evacuations were ordered in and around Wilkes-Barre, where the levee system is just high enough to hold back the river if it crests at the predicted level. Even if the levees hold, 800 to 900 unprotected homes were in danger. If they fail, thousands of buildings could be lost.

"This is a scary situation," said Stephen Bekanich, Luzerne County's emergency management director. He and other officials were confident the levees would work but sought volunteers to lay sandbags on both sides of the river.

In Hummelstown, another Pennsylvania community along the river, Donna MacLeod had to be rescued from her home.

"I'm heartsick," she said. "I know I lost two cars and everything that was in my basement and everything that was on the first floor. But I have my life and I have my dog, so that's good."

Upriver in Binghamton, N.Y., a city of about 45,000, the Susquehanna coursed into the streets and climbed halfway up lampposts at a downtown plaza. Mayor Matt Ryan said it was the city's worst flooding since the flood walls were built in the 1930s and `40s.

Road closures effectively sealed Binghamton off to outside traffic as emergency responders scrambled to evacuate holdouts who didn't heed warnings to leave. Buses and then boats were used to evacuate residents, and National Guard helicopters were on standby.

"It's going to get worse," Gov. Andrew Cuomo said, warning people to leave when they get the order.

Up to 20 centimetres of rain fell in parts of Pennsylvania, and a similar amount fell in Binghamton. Rivers and streams passed or approached flood stage from Maryland to Massachusetts, and experts said more flooding was coming.

The storm compounded the misery for some people still trying to bounce back from Hurricane Irene.

Some of the areas hardest hit by the August storm, such as Vermont, avoided the brunt of the latest bad weather. But in Paterson, N.J., where the Passaic River was rising, about 75 people were still in a shelter because of Irene.

"We just finished cleaning up after the flood from Irene," said Edith Rodriguez, who lived in shelters for three days and spent Wednesday night at a high school outside Schenectady, N.Y., because of Lee. "Now we have to start all over again."

Commuters and other travellers searched for detours as highways and other roads were flooded out, including sections of New York's Interstate 88, which follows the Susquehanna's path. In eastern Pennsylvania, where hundreds of roads were closed, flooding and a rock slide partially closed the Schuylkill Expressway, a major artery into Philadelphia.

Amtrak passenger service on New York's east-west corridor was cancelled, as were classes at many colleges and schools across the Northeast.

At least 11 deaths have been blamed on Lee: four in central Pennsylvania, two in northern Virginia and one in Maryland, along with four others killed when it came ashore on the Gulf Coast last week.

Pennsylvania Gov. Tom Corbett warned of "a public health emergency because sewage treatment plants are underwater and no longer working."

"Flood water is toxic and polluted," he said. "If you don't have to be in it, keep out."

Up to 75,000 residents in and around Wilkes-Barre were ordered to leave. The mayor told residents to pack food, clothing and medicine and plan for a three-day evacuation.