Superstorm Sandy has battered parts of the eastern United States, flooding major cities and killing at least 13 people.
The National Hurricane Centre, which reclassified the storm as 'post-tropical', said torrential rains and wind made landfall along the New Jersey coast near Atlantic City at around 8pm EDT (12am Irish time).
It brought gusts of more than 85mph (135kph) and a record-breaking 13ft surge of seawater in Manhattan, submerging road and subway tunnels.
New York University hospital was forced to move patients to other hospitals after it lost power and its back-up generator broke down.
Among them were 20 babies from neonatal intensive care - some on respirators operating on battery power.
Firefighters in New York said one man had been killed by a falling tree, while two people were also killed when a tree fell onto a vehicle in New Jersey.
A total of 12 people were reported dead by local officials in New York, New Jersey, Maryland, Pennsylvania, West Virginia and North Carolina, while in Toronto, Canada, police said a woman died after being hit by flying debris.
Mayor Michael Bloomberg told a news conference 250,000 Manhattan homes had been left without power by the storm, with electricity knocked out to more than six million Americans.
Amateur footage captured a large explosion at a power station near the island's near East 14th Street.
Mr Bloomberg said the worst of the storm had passed and that authorities expected the tidal surge to recede by 12am EDT on Wednesday.
But thousands of flights have been cancelled at airports in cities up and down the coast, causing widespread travel chaos.
British Airways axed all of its flights to and from New York, Newark, Baltimore, Washington DC, Boston and Philadelphia, and 11 of today's return flights to and from the East Coast have been cancelled.
It had been feared the surge of seawater could damage the underground electrical and communications lines in lower Manhattan that are vital to the nation's financial centre.
And the New York Stock Exchange and the Nasdaq suspended trading for a weather event for the first time since Hurricane Gloria in 1985.
Sandy, which killed 69 people in the Caribbean before making its way up the Atlantic, has seen subways, buses, trains and schools closed across a region of more than 50 million people from Washington to Boston.
As it made its way toward land, it converged with a cold-weather system that turned into a hybrid consisting not only of rain, high wind and snow.
Earlier, a US sailor on board a replica of the HMS Bounty was recovered from the sea in an "unresponsive" condition, and the captain was missing and feared dead after the tall ship went down off the Carolinas.
President Barack Obama and Republican rival Mitt Romney suspended their campaigning with just over a week to go before election day.
At the White House, Mr Obama had made a direct appeal to those at risk
"Please listen to what your state and local officials are saying," he said.
"When they tell you to evacuate, you need to evacuate. Don't delay, don't pause, don't question the instructions that are being given, because this is a powerful storm."