The 500-mile wide storm was expected to hit the city by early morning, bringing winds of around 85 mph (140km/h) and Mayor Michael Bloomberg ordered an unprecedented evacuation of 370,000 people in low-lying areas.
Five people have died on the east coast, including an 11-year-old boy killed in Newport News, Virginia, as winds toppled a tree and sent it crashing through a block of flats.
Thousands of residents and visitors fled resort towns along the New Jersey shore and mandatory evacuations covered all of the state’s barrier island beach resorts, including popular spots as Atlantic City, Cape May and Long Beach Island.
The American Red Cross was preparing dozens of emergency shelters along the east coast.
The National Guard has deployed 1500 members around the state to help with evacuations and assist at shelters where thousands had already arrived to ride out the storm.
More than two million people in the US have now been ordered to leave their homes and a state of emergency have been declared in North Carolina, Maryland, Virginia, Delaware, New Jersey, New York and Connecticut.
The greatest danger to New Yorkers is a potential tidal surge and residents were being warned to prepare for power outages and flooding.
New York City features a complex geography of islands and peninsulas surrounded by rivers, harbours and open sea making it vulnerable to a battering from the powerful storm.
Around 7000 hospital patients and nursing home residents were evacuated from facilities in vulnerable neighborhoods and a public transit system that moves 8.5 million people per week day was shut down as a precaution.
Authorities in New York said they would not arrest people in the affected low-lying areas who chose to stay, but Mayor Michael Bloomberg warned: “If you don’t follow this, people may die.”
“This is a life-threatening storm to people here. Staying behind is dangerous, staying behind is foolish and it’s against the law.”
However, despite the persistent warnings, the neighbourhood around Coney Island – also in the danger zone – was calm. Parked cars lined the streets, and there was no sign of an exodus.
City Councillor Michael Nelson said many people seemed unwilling to leave despite 50,000 being affected by the evacuation order.
President Barack Obama, who cut short his holiday to return to Washington, had a conference call about the hurricane with emergency officials yesterday.
He earlier warned Irene could be “a historic hurricane” and that everyone should take the storm seriously.
A first death caused by the storm was reported in North Carolina. Authorities said it blew a large tree branch onto a man near Raleigh, killing him.
The National Hurricane Center has downgraded Irene from a category two to a category one hurricane but says winds gusting up to 90mph extend outwards some 90 miles from the eye of the storm. Tropical-force winds extend as far as 290m.