Tens of thousands of residents were ordered to evacuate coastal areas in the north eastern United States today as big cities and small towns across the US Northeast braced for the onslaught of a superstorm threatening some 60 million people along the most heavily populated corridor in the nation.
"The time for preparing and talking is about over," Federal Emergency Management Administrator Craig Fugate warned as a monster Hurricane Sandy headed up the Atlantic Coast on a collision course with two other weather systems. "People need to be acting now."
New York City announced its subways, buses and trains would stop running tonight, and its 1.1 million-student school system would be closed tomorrow.
Mayor Michael Bloomberg also ordered the evacuation of part of lower Manhattan and other low-lying neighbourhoods.
"If you don't evacuate, you are not only endangering your life, you are also endangering the lives of the first responders who are going in to rescue you," Mr Bloomberg said. "This is a serious and dangerous storm."
Tens of thousands of people along the coast in Delaware, New Jersey, Connecticut and other threatened areas were also under orders to clear out because of as much as 30cms of rain, punishing winds of 130 kph, and a potentially deadly wall of water four to 1.2 to 3.3 metres high.
President Barack Obama met federal emergency officials for an update on the storm's path and the danger it poses.
Mr Obama said that Sandy is a "serious and big storm" that will be slow-moving and might take time to clear up. The government would "respond big and respond fast" after it hits, he said.
Sandy was headed north from the Caribbean, where it left at least 65 people dead, mostly in Haiti, and was expected to hook left toward the mid-Atlantic coast and come ashore late tomorrow or early Tuesday, most likely in New Jersey, colliding with a wintry storm moving in from the west and cold air streaming down from the Arctic.
Forecasters warned that the resulting megastorm could wreak havoc over 800 miles (1,300kms) from the East Coast to the Great Lakes. Parts of West Virginia, Virginia, Kentucky and North Carolina could get snow - 60 cms or more in places.
The danger was hardly limited to coastal areas, with officials worried about inland flooding. They also warned that the rain could saturate the ground, causing trees to topple onto power lines and cause blackouts that could last for several days.
States of emergency were declared from North Carolina, where gusty winds whipped steady rain on Sunday morning, to Connecticut. Delaware ordered 50,000 people in coastal communities to clear out by 8pm tonight local time.
Officials in New York City were particularly worried about the possibility of subway flooding. The city closed the subways before Hurricane Irene last year, and a Columbia University study predicted that an Irene surge just 30cms higher would have paralysed lower Manhattan.
However, the New York Stock Exchange planned to open for trading as usual tomorrow, despite fears that flooding would damage the underground electrical network that is so vital to the nation's financial centre.
Sandy was at Category 1 strength, packing 120 kph winds, about 435 kms southeast of Cape Hatteras, North Carolina, and moving northeast at 22.5 kph as of 2pm (1800 GMT) today, according to the National Hurricane Centre in Miami. It was about 925 kms south of New York City.
But the storm was so big that forecasters could not say with any certainty which areas would get the worst of it.
Bobbie Foote said she would heed an evacuation order for south Wilmington, Delaware, and would take shelter at her daughter's home in nearby Newark.
"My daughter insists that I leave this time," said Ms Foote, a 58-year-old fitness coach. It will be the first time she has fled a storm threatening the apartment building that has been her home for at least 40 years in the working-class neighbourhood near the Delaware River.
She said she stayed last year when flooding from the remnants of Hurricane Irene blocked streets at either end of the neighbourhood. She said her daughter wouldn't stand for her getting trapped that way again.
"She said I should never put myself in that predicament where I cannot get in or out of where I live," she said.
Amtrak began cancelling passenger train services last night to parts of the East Coast, including between Washington and New York. Airlines started moving planes out of airports to avoid damage and added Sunday flights out of New York and Washington in preparation for flight cancellations tomorrow.
The Virginia National Guard was authorised to call up to 500 troops to active duty for debris removal and road-clearing, while homeowners stacked sandbags at their front doors in coastal towns.
In North Carolina's Outer Banks, there was some scattered, minor flooding at daybreak today on the beach road in Nags Head. The bad weather could pick up there later in the day, with the major concerns being rising tides and pounding waves.
In New Jersey, hundreds of coastal residents started moving inland.
Governor Chris Christie's emergency declaration will force the shutdown of Atlantic City's 12 casinos for only the fourth time in the 34-year history of legalised gambling there. City officials said they would begin evacuating the gambling hub's 30,000 residents at noon, bussing them to mainland shelters and schools.
The storm also forced the presidential campaign to juggle schedules.
Republican challenger Mitt Romney scrapped plans to campaign in Virginia and switched his schedule for the day to Ohio.
First lady Michelle Obama cancelled an appearance in New Hampshire for Tuesday, and Barack Obama moved a planned tomorrow departure for Florida to tonight to beat the storm. He also cancelled appearances in Northern Virginia tomorrow and Colorado on Tuesday.