Brattleboro, Vermont (CNN) -- The torment from Irene isn't over as parts of the Northeast grapple with dangerous floodwaters, widespread power outages and stranded residents.
At least 21 deaths across eight states were blamed on Irene, which had fizzled to a post-tropical cyclone and was headed over eastern Canada by Monday morning.
Some of the biggest, continuing headaches involved flooding, as tidal storm surges and overflowing, fast-moving rivers left homes in North Carolina and points northward awash.
More flooding is predicted in New Jersey as rivers crest.
And in Plattsville, New York, seven families who thought they had escaped the wrath of Irene were stranded in the Catskill Mountains after bridges crumbled all around them.
But parts of New York City will return to normal Monday, as some subway services will resume and the three major airports in the area will open.
The U.S. government estimated that the cost from wind damage alone is expected to top $1 billion, with downed power lines leaving more than 4 million people without electricity.
"The impacts of this storm will be felt for some time, and the recovery effort will last for weeks or longer," President Barack Obama said Sunday evening from Washington.
Numerous "swift-water" rescue teams were dispatched Sunday night around Vermont, where state emergency management spokesman Mark Bosma said some small towns were "entirely covered with water" and people, including a woman who was in labor, were stranded in schools and cars.
Vermont State Police Capt. Ray Keefe said Wilmington is "cut off," hundreds of roads had been closed, and some homes were washed off foundations and into lakes.
Initial fears about coastal flooding in New Jersey -- which had prompted the evacuation of more than 1 million people from the shore -- had given way to fresh concerns about inland flooding.
That left many residents like Guy Pascarello, whose family's Secaucus home of 40 years was declared uninhabitable after it became inundated by three-foot-high waters, trying to figure out what to do next.
"I don't know (what we'll do), this is all new ground," Pascarello said. "The good news is that it's just stuff. This is a home and we love our home, but it's just things."
Even locations well inland, like Princeton Junction about halfway between New York City and Princeton, had waters as high as 12 feet that covered roads and bridges, resident Edward Picco said.
"It's crazy. ... The water is moving between buildings, up, down, all sorts of different directions," Rich Graessle said from Millburn, New Jersey, on Sunday.
Along the shore in Long Beach, New York, water poured underneath the boardwalk and into the city's downtown.
Outside Philadelphia, meanwhile, waters climbed to street-sign levels in Darby, with the water sending "couches, furniture, all kinds of stuff floating down the street," Philadelphia Mayor Michael Nutter said. Two buildings collapsed in Philadelphia, Nutter told reporters, but no one was injured.
It's all due to a storm that first made landfall at 7:30 a.m. Saturday in North Carolina, paralleled the coast, and slammed into Little Egg Inlet, New Jersey on Sunday morning, the National Hurricane Center said.
Officials have reported six deaths in North Carolina, four in Virginia, four in Pennsylvania, two in New York and one each in Connecticut, Maryland, Florida, New Jersey. Authorities are trying to determine whether another death reported in New York is connected to the storm.
In addition, one woman is "feared dead" in Vermont after being swept away in raging waters in Wilmington, Bosma said.
Connecticut emergency management spokesman Scott Devico said one man has been reported missing in river-waters in the inland town of Bristol, while two individuals are unaccounted for in East Haven because authorities do not know their whereabouts after their home got swept away by the sea.
And the governor of Virginia, parts of which saw 16 inches of rain and top winds clocked at 83 mph, warned Sunday that more bad news may be coming.
"Undoubtedly, there will be more reports of damage, of injuries, perhaps fatalities," Gov. Bob McDonnell told reporters.
FEMA director Craig Fugate vowed Sunday that authorities will work with those impacted by the wind, rain, storm surge and resulting flooding.
"When the disaster comes off the news and no one is paying attention, we still don't go home," he said. "We know we've got a lot of work ahead of us."
