New York City's transit system shut down last night and mandatory evacuation orders were issued for swaths of the mid-Atlantic coast as a potentially calamitous storm barrelled down on a region of 60 million inhabitants.
Governor Andrew Cuomo announced that train, subway and bus services would close at 7pm local time (11 pm GMT).
Michael Bloomberg, the city's Mayor, ordered the evacuation of low-lying areas including parts of Manhattan. Up to 375,000 people may have to leave their homes and schools will be shut. "This is a serious and dangerous storm," he said.
Across a dozen states, including several that are pivotal in the presidential race, emergency measures are in place for the arrival of Hurricane Sandy, including the mobilisation of National Guardsmen and the deployment of repair crews from unaffected parts of the country, to cope with the widespread power cuts expected.
"The time for preparing and talking is about over," Craig Fugate, head of Fema, the federal disaster-management agency, warned after a conference call with Barack Obama, who was aboard Air Force One on the campaign trail, and other officials. "People need to be acting now."
New Yorkers appeared to be largely unperturbed yesterday afternoon. In Manhattan's West Village, residents queuing at local grocery stores appeared to be going about their usual Sunday shop – though many carts and baskets were weighed down by packs of bottled water.
Mr Bloomberg ordered the evacuation of the city's Zone A, encompassing parts of the southern Manhattan coastline, areas along the East River in Brooklyn, Hamilton Beach, the Rockaways to the south-east, and other exposed regions. In Washington, authorities urged people to bring Halloween decorations indoors, warning that even pumpkins could be picked up by the winds and turned into flying cannonballs.
The storm – which has already killed 66 people as it cut a path across the Caribbean – is to make landfall along the New Jersey and Delaware coast.
Forecasters predict 4in to 10in of rain and potentially destructive coastal storm surges of 4ft to 8ft, threatening widespread flooding in low-lying parts of cities such as Baltimore and Washington DC.