NEW YORK — Top developments:
- Storm moves into New England
- FEMA chief warns people of dangers even after Irene passes
- At least 20 deaths blamed on Irene
- 4 million without power in Eastern states
- More than 10,000 flights canceled through Monday
Irene charged into New England on Sunday as it weakened to a tropical storm after racing across a shuttered New York City and leaving behind a stunned U.S. East Coast where at least 20 people died. Severe flooding was widespread and 4 million homes and businesses lost power.
As waves continued pounding the Connecticut shore east of America's biggest city, New York City Mayor Michael Bloomberg lifted the evacuation order for residents in low-lying areas.
New England residents were now feeling the brunt of the diminished but still-dangerous storm, which will cause flooding and winds that could topple many towering trees anchored in soil already saturated by earlier heavy rains. The storm was centered about 65 miles south of Rutland, Vermont at about 5 p.m. EDT, and it was moving north-northeast at about 26 mph.
Forecasters expect it to reach Canada later Sunday or early Monday. Irene, while diminished in strength, was still massive and powerful, carrying sustained winds of 50 mph after its long journey up the East Coast, where it dropped a foot of rain on North Carolina and Virginia. The National Hurricane Center downgraded the storm after its winds fell below 74 mph, the threshold for a hurricane.
As the eye of the sprawling storm blew through America's largest city and Long Island to the east, it pushed an 8-foot Atlantic storm surge toward New York and sent salty floodwater flowing into lower Manhattan.
Nearly 1 million homes and businesses in New York state were without power, authorities said.
President Barack Obama Sunday warned that flooding from Hurricane Irene could worsen as rivers flood their banks and said federal recovery efforts would last a few weeks.
"I want people to understand this is not over," Obama said in a statement read at the White House. "Response and recovery efforts will be an ongoing operation," he added.
His comments echoed those of Homeland Security Secretary Janet Napolitano earlier. She told a news conference that pre-storm preparations dramatically reduced the loss of life but warned that river flooding across the eastern seaboard continued to pose hazards for the public.
Interactive: Hurricane Tracker (on this page)
65 million people affected
Forecasters said early Sunday that Irene was moving to the north-northeast at 26 mph as it pushed into New England. Officials also warned that isolated tornadoes were possible in the northeast.
The huge storm had threatened 65 million people up and down the Atlantic coast, estimated as the largest number of Americans ever affected by a single storm.
The 20 deaths related to Irene included two children, an 11-year-old boy in Virginia killed when a tree crashed into his home and a North Carolina child who died in a car crash at an intersection where traffic lights were out. Four other people were killed by falling trees or tree limbs — two in separate Virginia incidents, one in North Carolina and one in Maryland. A surfer and another beachgoer in Florida were killed in heavy waves.Video: Bad, but could have been worse (on this page)
The body of a 27-year-old man was found in the Cape Fear River, the sheriff's office said on Sunday, reported StarNews Online. The man had last been seen in the river Saturday afternoon when he either fell or jumped in, the report said.
In New York, state police recovered a woman's body from the Onesquethaw Creek in the Town of New Scotland, NBC reported Sunday evening. The woman's husband reported her missing at about noon, and police said they believed it to be related to the storm because the creek overflowed earlier in the day.
In Vermont a woman was swept away by the Deerfield River, and is presumed dead, though no body has been found, according to the Burlington Free Press.
A New Jersey firefighter was in critical condition after injuries sustained when he was attempting a water rescue. New Jersey's Gov. Christie stated at a press briefing that the first responder had died; his office said later that the governor had received erroneous information.
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New York City was eerily quiet. In a city where many people don't own cars, the population stayed indoors. The entire transit system was shut down because of weather for the first time ever. All of the city's airports were closed. Broadway shows, baseball games and other events were all canceled or postponed.
But in a briefing Sunday afternoon, Mayor Michael Bloomberg indicated that the city was moving into recovery mode.
He said there were no known deaths or injuries caused by Irene in New York City.
"The good news is the worst is over," Bloomberg said.
"As we anticipated, the storm surge has caused serious flooding across the five boroughs, including here in Lower Manhattan, where the East and Hudson Rivers are flowing over their banks and into the parks and low-lying streets at the water's edge," said Bloomberg. "We did have substantial erosion at the Staten Island beaches and in the Rockaways, where the waves breached 94th Street between 127th and 132nd Streets."
He said the city government would reopen on Monday, despite some damage to city government buildings.
NBC reported that the city's three airports were slated to reopen sometime Monday, according to the New York Port Authority.
The stock exchange and other financial institutions are also to reopen on time Monday morning.
For many people, however, getting to work would remain a problem until the subway and other transit systems were back up and running.
Bloomberg praised the residents of New York for their cooperation in the face of the hurricane. Despite dire predictions, he said there were just 45 arrests overnight, compared to an average of 345 on a normal Saturday night in the city.
Video: Jersey shore battered, but inland might have it worse (on this page)
New Jersey Gov. Chris Christie said in an interview on NBC's "Meet the Press" that the storm covered half of the state and 250 roads were closed due to flooding and downed trees.
Christie said he expects damages from Irene to be costly along the Atlantic coast and from inland river flooding.
"I've got to imagine that the damage estimates are going to be in the billions of dollars, if not in the tens of billions of dollars," Christie said.
An analyst cited by The New York Times said the total damage inflicted by Irene may reach $7 billion, which according to the report would put it among the 10 costliest catastrophes.
Newspaper stands float down NYC streets
Briny water from New York Harbor submerged parts of a promenade at the base of Manhattan. A foot of water rushed over the wall of a marina in front of the New York Mercantile Exchange, where gold and oil are traded.
"You could see newspaper stands floating down the street," said Scott Baxter, a hotel doorman in the SoHo neighborhood.
As the center of the storm passed over Central Park at midmorning, floodwater reached the wheel wells of some stranded cars in Manhattan, and more streamed into the streets of Queens.
Still, the storm didn't come close to inflicting the kind of catastrophic damage that had been feared in the city. The Sept. 11 museum, a centerpiece of the rebuilding of the World Trade Center site, said on Twitter that none of its memorial trees were lost.
Forecasters had said there was a chance a storm surge on the fringes of Lower Manhattan along New York Harbor could send sea water streaming into the maze of underground vaults that hold the city's cables and pipes, knocking out power to thousands and crippling the city. Officials' feared water would slosh into Wall Street, the ground zero location of the former Twin Towers and the luxury high-rise apartments of Battery Park City.
Battery Park City in the extreme south of Manhattan island was virtually deserted as rain and gusty winds pummeled streets and whipped trees. Officials were bracing for a storm surge of several feet that could flood or submerge the Promenade along the Hudson River. On Wall Street, sandbags were placed around subway grates near the East River because of fear of flooding.
In Times Square, shops boarded up windows and sandbags were stacked outside of stores. Construction at the World Trade Center site came to a standstill.
Some cabs still on streets
While public transit was shut down, some taxi cabs could be found.
"I have to work. I would lose too much money," said cabbie Dwane Imame, who worked through the night. "There have been many people, I have been surprised. They are crazy to be out in this weather."
In New York City, 370,000 people had been ordered to move to safer ground, although they appeared in great numbers to have stayed put.
"It's nasty out there and wet," Cindy Darcy said from a 36-floor building facing the harbor. "We unplugged the drains, and we fastened anything loose or removed it." She was up early making bagels for the nine workers and 24 inhabitants who stayed in the building, which is in the evacuation zone.
New York has seen only a few hurricanes in the past 200 years. The Northeast is much more accustomed to snowstorms — including a blizzard last December, when Mayor Michael Bloomberg was criticized for a slow city response.
Irene made landfall just after dawn Saturday near Cape Lookout, North Carolina, at the southern end of the Outer Banks. Shorefront hotels and houses were lashed with waves, two piers were destroyed and at least one hospital was forced to run on generator power.PhotoBlog: Eye of the storm
Millions of air travelers likely affected
All three New York airports remained effectively closed Sunday morning.
More than 10,000 flights have been canceled through Monday, according to FlightAware. That includes some 6,600 on Sunday alone. The number of airline passengers affected by the storm could easily be in the millions because so many flights make connections on the East Coast.
Amtrak, the nation's only long haul passenger rail service, canceled all Northeast trains for Sunday.
Irene caused flooding from North Carolina to Delaware, both from the 7-foot waves it pushed into the coast and from heavy rain.
More than 1 million of the homes and businesses without power were in Virginia and North Carolina, which bore the brunt of Irene's initial fury. Then the storm knocked out power overnight to hundreds of thousands in Washington, Maryland, Delaware, Pennsylvania, New Jersey, the New York City area and Connecticut.Readers capture Hurricane Irene's approach
Irene was the first hurricane to make landfall in the continental United States since 2008, and came almost six years to the day after Katrina ravaged New Orleans and the Gulf Coast.
In New Jersey, the Oyster Creek nuclear plant, just a few miles from the coast, shut down as a precaution as Irene closed in. And Boston's transit authority said all bus, subway and commuter rail service were suspended Sunday.
There was an evacuation order put in place for this part of Connecticut but not all people heeded the orders and left, she said. Rescue teams were checking the homes for people.
In addition, there are currently 12,000 people without power in Fairfield alone and 70 people are in shelters
NBC News, msnbc.com, The Associated Press and Reuters contributed to this report.