New York authorities ordered the evacuation Sunday of 375,000 people from low-lying coastal areas as the imminent arrival of Hurricane Sandy forced the entire eastern seaboard into lockdown mode.
More than 7,400 flights out of east coast hubs were canceled and ground transport was due to grind to a halt on as non-essential government staff were told not to show up for work and public schools were shuttered.
Amtrak suspended all bus and train services up and down the coast. Subway services, buses and commuter trains were also shut down in New York, Philadelphia and Washington.
And the New York Stock Exchange said it will be completely closed on Monday, and possibly on Tuesday.
Hundreds of thousands of residents in low-lying coastal areas were under orders to clear out and an AFP reporter said the beach resort of Rehoboth in Delaware was a ghost town as the deadline passed for mandatory evacuation.
The storm made its presence felt on the knife-edge US presidential race as President Barack Obama's jittery campaign voiced fears about turnout on November 6 and both candidates pulled out of rallies in must-win states.
"My first message is to all people across the eastern seaboard, mid-Atlantic going north. You need to take this very seriously," Obama said, urging 50 million Americans across the region to heed the advice of local authorities.
The president, who spoke after being briefed at the headquarters of the Federal Emergency Management Agency (FEMA), cautioned that Sandy was a slow-moving storm that certain areas would take a long time to recover from.
"The time for preparing and talking is about over," FEMA administrator Craig Fugate warned. "People need to be acting now."
As some defiant New Yorkers stocked up on beer and laughed off the evacuation orders saying they intended to ride out the storm, the National Weather Service office in neighboring New Jersey held no punches in its warning to residents.
"If you are reluctant to evacuate, and you know someone who rode out the '62 storm on the Barrier Islands, ask them if they could do it again," a bulletin said, referring to the notorious Ash Wednesday storm of 1962.
"If you are reluctant, think about your loved ones, think about the emergency responders who will be unable to reach you when you make the panicked phone call to be rescued, think about the rescue/recovery teams who will rescue you if you are injured or recover your remains if you do not survive."
Fearful residents from Washington to New York to Boston queued for emergency provisions like bottled water and batteries in long lines that stretched out the doors of supermarkets.
A 'nor-easter on steroids'
After laying waste to parts of the Caribbean, where it claimed 66 lives, most of them in Cuba and Haiti, Hurricane Sandy was predicted to come crashing ashore in New Jersey and Delaware late Monday or early Tuesday.
Packing hurricane force winds upwards of 75 miles per hour (120 kilometers per hour), the storm was about 470 miles (760 kilometers) south southeast of New York early Monday and beginning to turn west, the National Hurricane Center said.
Winds stretched more than 520 miles (835 kilometers) from its eye, meaning everywhere from South Carolina to southern Canada was due to be affected.
"The system is so large that I would say millions of people are at least in areas that have some chance of experiencing either flash flooding or river flooding," National Hurricane Center director Rick Knabb warned.
Forecasters cautioned that the massive storm was far larger and more dangerous than last year's devastating Hurricane Irene that claimed 47 lives and caused an estimated $15 billion in damage.
Current projections show Sandy barreling north on a collision course with two other weather systems that would send it hooking into the Delaware or New Jersey coast as one of the worst storms on record.
Weather experts say the collision could create a super-charged storm bringing floods, high winds and even heavy snow across a swath of eastern states and as far inland as Ohio.
Governors have declared states of emergency in Connecticut, Delaware, Maryland, Massachusetts, New Jersey, New York, North Carolina, Pennsylvania, Vermont, Virginia and the US capital Washington.
Obama signed emergency declarations to free up federal disaster funds for New York state, Massachusetts, Maryland and Washington, New Jersey and Connecticut.