Hurricane Sandy is closing in on highly populated areas of the US East Coast, threatening storm surges and devastating flooding.
In New York City, thousands have been ordered to evacuate, and shelters have been set up in 76 schools.
Public transport in Washington DC, Philadelphia and New York is suspended and the New York Stock Exchange shut.
Forecasters fear Sandy will become a super-storm when it collides with cold weather fronts from the west and north.
It also coincides with a full moon, which is bringing higher tides.
Sandy has already killed 60 people after sweeping through the Caribbean in the past week.
Campaigning for the US presidential election has also been disrupted, eight days ahead of election day on 6 November.
At the scene
At Battery Park City on the southern tip of Manhattan, the water is already lapping over my boots. It’s only mid-morning, hours before Hurricane Sandy is due to make landfall, and the sea is swelling.
Tonight with the storm surge the water levels are expected to rise, though already it seems to me the water is as high as it was during Hurricane Irene last year. The city is eerily quiet. The Nasdaq sign at Times Square was blank – even the stock exchange isn’t trading.
The subways are shut, grocery stores have signs up saying they’ve already run out of food. The city is braced for what could be the worst storm in a generation. At this point the preparations have been made – sandbags are everywhere in lower Manhattan. All anyone can do is wait, anxiously.
At 11:00 EDT (15:00 GMT), Sandy was churning about 260 miles (415km) south-east of New York City, the National Hurricane Center (NHC) said.
The storm had strengthened from the morning, with maximum sustained winds clocked at 90mph (150km/h) with higher gusts.
Hurricane force winds extended for 175 miles and tropical storm force winds for 485 miles, the NHC added.
The vast hurricane, about 520 miles across, is moving slowly north-west and could linger over as many as 12 states for 24-36 hours, bringing up to 10in (25cm) of rain, 24in of snow, extreme storm surges and power cuts.
At least 14 out of 16 people on board a replica of HMS Bounty – built for the 1962 film Mutiny on the Bounty – have been rescued, the US Coast Guard says.
They were plucked from two life rafts off the coast of North Carolina after abandoning ship. The Coast Guard is searching for the missing crew members.
The eye of the storm is expected to move across the coast of mid-Atlantic states by Monday night, the NHC said.
Due to hit the US East Coast just before Halloween, it has been dubbed “Frankenstorm”.
Amtrak has suspended passenger train services across the north-east and air travel has been badly hit, with some 7,500 flights cancelled.
With public transport suspended across the region, many workers stayed at home on Monday.
In New York, taxi driver Peter Franklin told the BBC that the city was “shut down”.
“I feel like I am living in a science fiction movie,” he said.
Hundreds of thousands of people from Maryland to Connecticut were ordered to leave low-lying coastal areas.
They included about 375,000 residents in lower Manhattan and other areas of New York City and another 30,000 in Atlantic City, New Jersey.
There are already reports of flooding in Atlantic City.
President Barack Obama declared emergencies in Massachusetts, Connecticut, Rhode Island, New York, New Jersey and Pennsylvania.
He pulled out of a planned rally in Florida with former President Bill Clinton on Monday and headed back to the White House to monitor emergency operations. The campaign also cancelled an event scheduled for Tuesday in Wisconsin, far from the storm.
Visiting the Federal Emergency Management Agency (Fema) in Washington on Sunday, President Obama vowed the government would “respond big and respond fast” after Sandy had passed.
Authorities warned that high tides triggered by a full moon could create storm surges of up 11ft (3m), sending seawater surging through parts of lower Manhattan.
The United Nations headquarters in New York has also been shut down. The East River in New York City has begun overflowing its banks on the Brooklyn side.
New York City Mayor Michael Bloomberg described it as “a serious and dangerous storm”.
“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,” he said.
New Jersey Governor Chris Christie advised residents of that state: “Don’t be stupid. Get out.”
Some 200 National Guardsmen will patrol Manhattan and 300 more will be deployed in Long Island.
Links : BBC News