The warning from officials to anyone who might be affected path was simple: Be prepared and get out of the way.
Hurricane Sandy was headed north from the Caribbean, where it left nearly five dozen dead, to meet a winter storm and a cold front, plus high tides from a full moon, and experts said the rare hybrid storm that results will cause havoc over 800 miles from the East Coast to the Great Lakes.
"I've been here since 1997, and I never even put my barbecue grill away during a storm," Russ Linke said shortly before he and his wife left Ship Bottom on Saturday. "But I am taking this one seriously. They say it might hit here. That's about as serious as it can get."
He and his wife secured the patio furniture, packed the bicycles into the pickup truck, and headed off the island.
The danger was hardly limited to coastal areas. Forecasters were far more worried about inland flooding from storm surge than they were about winds. Rains could saturate the ground, causing trees to topple into power lines, utility officials said, warning residents to prepare for several days at home without power.
States of emergency were declared from North Carolina, where steady rains were whipped by gusting winds Saturday night, to Connecticut. Delaware ordered mandatory evacuations for coastal communities by 8 p.m. Sunday.
Officials were particularly worried about the possibility of subway flooding in New York City, said Louis Uccellini, head of environmental prediction for the National Oceanic and Atmospheric Administration.
Sandy was at Category 1 strength, packing 75 mph winds, about 260 miles southeast of Cape Hatteras, N.C., and moving northeast at 10 mph as of 8 a.m. Sunday, according to the National Hurricane Center in Miami. It was about 395 miles south of New York City.
The storm was expected to continue moving parallel to the Southeast coast most of the day and approach the coast of the mid-Atlantic states by Monday night, before reaching southern New England later in the week.
The storm was so big, however, and the convergence of the three storms so rare, that "we just can't pinpoint who is going to get the worst of it," said Rick Knabb, director of the National Hurricane Center in Miami.
"You never want to be too naive, but ultimately, it's not in our hands anyway," said Andrew Ferencsik, 31, as he purchased plywood and 2-by-4 lumber from a Home Depot in Lewes, Del.
New Jersey Gov. Chris Christie, who was criticized for not interrupting a vacation in Florida while a snowstorm pummeled the state in 2010, broke off campaigning for Republican presidential nominee Mitt Romney in North Carolina on Friday to return home.
"I can be as cynical as anyone," said Christie, who declared a state of emergency Saturday. "But when the storm comes, if it's as bad as they're predicting, you're going to wish you weren't as cynical as you otherwise might have been."
Up and down the Eastern Seaboard and far inland, officials urged residents and businesses to prepare in ways big and small.
New York Gov. Andrew Cuomo told the Metropolitan Transportation Authority to prepare to shut the New York City's subways, buses and suburban trains. The city closed the subways before Hurricane Irene last year, and a Columbia University study predicted that an Irene surge just 1 foot higher would have paralyzed lower Manhattan.
Amtrak began canceling train service Saturday night to parts of the East Coast, including between Washington and New York. Airlines started moving planes out of airports to avoid damage and adding Sunday flights out of New York and Washington in preparation for flight cancellations on Monday.
The Virginia National Guard was authorized to call up to 500 troops to active duty for debris removal and road-clearing, while homeowners stacked sandbags at their front doors in coastal towns.
President Barack Obama was monitoring the storm and working with state and locals governments to make sure they get the resources needed to prepare, administration officials said.
In North Carolina's Outer Banks, a group of about 20 people was forced to wait out the storm on Portsmouth Island, a former fishing village that is now uninhabited and accessible only by private ferry.
"We tried to get off the island and the ferry service shut down on us," said Bill Rowley, 49, of Rocky Mount, N.C.
Rowley said he could see 15-foot seas breaking over the island's dunes, enough to bring water to the island's interior.
"We'll be inundated and it'll probably be worse tomorrow," he said.
In New Jersey, hundreds of coastal residents started moving inland. Christie's emergency declaration will force the shutdown of Atlantic City's 12 casinos for only the fourth time in the 34-year history of legalized gambling here. City officials said they would begin evacuating the gambling hub's 30,000 residents at noon Sunday, busing them to mainland shelters and schools.
The storm also forced the presidential campaign to juggle schedules. Romney scrapped plans to campaign Sunday in Virginia and switched his schedule for the day to Ohio. First lady Michelle Obama canceled an appearance in New Hampshire for Tuesday, and Obama moved a planned Monday departure for Florida to Sunday night to beat the storm. He also canceled appearances in Northern Virginia on Monday and Colorado on Tuesday.
Eighty-five-year-old former sailor Ray Leonard had a bit of advice for those in the path of the storm. Leonard and two crewmates in his 32-foot sailboat, Satori, rode out 1991's infamous "perfect storm," made famous by the Sebastian Junger best-selling book of the same name, before being plucked from the Atlantic off Martha's Vineyard, Mass., by a Coast Guard helicopter.
"Don't be rash," Leonard said Saturday from his home in Fort Myers, Fla. "Because if this does hit, you're going to lose all those little things you've spent the last 20 years feeling good about."
Breed reported from Raleigh, N.C. Contributing to this report were AP Science Writer Seth Borenstein in Washington; Emery Dalesio in Kill Devil Hills, N.C.; Karen Matthews and Samantha Bomkamp in New York; Randall Chase in Lewes, Del.; and Nancy Benac in Washington.