NEW YORK (AP) — Big cities from Washington to Boston braced Sunday for the onslaught of a superstorm that could menace 50 million people in the most heavily populated corridor in the US, with forecasters warning New York could be in particular peril.

Federal Emergency Management Administrator Craig Fugate warned that the “time for preparing and talking is about over,” as Hurricane Sandy made its way up the Atlantic on a collision course with two other weather systems that could turn it into one of the most fearsome storms on record in the US.

“People need to be acting now,” he said.

Forecasters warned that the megastorm could wreak havoc over 800 miles (1,300 kilometers) from the East Coast to the Great Lakes. States of emergency were declared from North Carolina to Connecticut.

Airlines canceled more than 7,600 flights and Amtrak began suspending passenger train service across the Northeast. New York and Philadelphia moved to shut down their subways, buses and commuter trains Sunday night and announced that schools would be closed on Monday. Boston, Washington and Baltimore also called off school.

As rain from the leading edges of the monster hurricane began to fall over the Northeast, tens of thousands of people in coastal areas from Maryland to Connecticut were under orders to clear out Sunday. That included 50,000 in Delaware alone and 30,000 in Atlantic City, New Jersey, where the city’s 12 casinos were forced to shut down for only the fourth time in the 34-year history of legalized gambling there.

Authorities warned that the biggest US city could get hit with an 11-foot (3.3-meter) wall of water that could swamp parts of lower Manhattan, flood subway tunnels and cripple the network of electrical and communications lines that are vital to the nation’s financial center.

Sandy, a Category 1 hurricane, is about 470 miles (756 kilometers) southeast of New York City and the center of the storm is expected to be near the mid-Atlantic coast on Monday night.

The National Hurricane Center said late Sunday night that the storm has top sustained winds of 75 mph (121 kph), with higher gusts. It is moving toward the northeast at 14 mph (23 kph). Hurricane-force winds extend up to 175 miles (284 kilometers) from the storm’s center.

Sandy was expected to hook left toward the mid-Atlantic coast and come ashore late Monday or early Tuesday, most likely in New Jersey, colliding with a wintry storm moving in from the west and cold air streaming down from the Arctic.

Forecasters said the monster combination could bring close to a foot (30 centimeters) of rain, a potentially lethal storm surge and punishing winds extending hundreds of miles (kilometers) outward from the storm’s center. It could also dump up to 2 feet (60 centimeters) of snow in Kentucky, North Carolina and West Virginia.

Louis Uccellini, environmental prediction chief for the National Oceanic and Atmospheric Administration, told The Associated Press that given Sandy’s east-to-west track into New Jersey, the worst of the storm surge could be just to the north, in New York City, Long Island and northern New Jersey.

Forecasters said that because of giant waves and high tides made worse by a full moon, the metropolitan area of about 20 million people could get slammed with an 11-foot (3.3-meter) wall of water.

“This is the worst-case scenario,” Uccellini said.

New York Mayor Michael Bloomberg warned people in low-lying areas of lower Manhattan and Queens to get out.

“If you don’t evacuate, you are not only endangering your life, you are also endangering the lives of the first responders who are going in to rescue you,” he said. “This is a serious and dangerous storm.”

New Jersey’s famously blunt Gov. Chris Christie was less polite: “Don’t be stupid. Get out.”

New York called off school Monday for the city’s 1.1 million students and announced it would suspend all train, bus and subway service Sunday night because of the risk of flooding, shutting down a system on which more than 5 million riders a day depend.

The New York Stock Exchange announced it will close its trading floor Monday but continue to trade electronically, despite fears from some experts that flooding could knock out the underground network of power, phone and high-speed Internet lines that are vital to the nation’s financial capital.

Officials also postponed Monday’s reopening of the Statue of Liberty, which had been closed for a year for $30 million in renovations.

In Washington, President Barack Obama promised the government would “respond big and respond fast” after the storm hits.

“My message to the governors as well as to the mayors is anything they need, we will be there, and we will cut through red tape. We are not going to get bogged down with a lot of rules,” he said.

He also pleaded for neighborliness: “In times like this, one of the things that Americans do is we pull together and we help out one another And so, there may be elderly populations in your area. Check on your neighbor, check on your friend. Make sure that they are prepared. If we do, then we’re going to get through this storm just fine.”

The storm forced the president and Republican rival Mitt Romney to rearrange their campaign schedules in the crucial closing days of the presidential race. And early voting on Monday in Washington and Maryland was canceled.

Shelters across the region began taking in people.

“We were told to get the heck out. I was going to stay, but it’s better to be safe than sorry,” said Hugh Phillips, who was one of the first in line when a Red Cross shelter in Lewes, Delaware, opened at noon.

“I think this one’s going to do us in,” said Mark Palazzolo, who boarded up his bait-and-tackle shop in Point Pleasant Beach, New Jersey, with the same wood he used in past storms, crossing out the names of Hurricanes Isaac and Irene and spray-painting “Sandy” next to them. “I got a call from a friend of mine from Florida last night who said, ‘Mark. Get out! If it’s not the storm, it’ll be the aftermath. People are going to be fighting in the streets over gasoline and food.’”

At least twice as many train passengers as usual crowded the Amtrak waiting area Sunday morning at New York’s Penn Station. Many were trying to leave New York earlier than planned.

The noon and 1 p.m. trains to Boston were sold out. Randall Ross, a bookseller from Shreveport, Louisiana, and his traveling companion, Mary McCombs, were waiting for an Amtrak train to Syracuse, the destination they chose after attempts to book flights through eight other cities failed.

“I just want to be somewhere else except New York City,” said McCombs, who will stay with friends in Syracuse until she and Ross can get a flight. “I don’t want to risk it.”

Despite the dire warnings, some souls were refusing to budge.

Jonas Clark of Manchester Township, New Jersey — right in the area where Sandy was projected to come ashore — stood outside a convenience store, calmly sipping a coffee and wondering why people were working themselves “into a tizzy.”

“I’ve seen a lot of major storms in my time, and there’s nothing you can do but take reasonable precautions and ride out things the best you can,” said Clark, 73. “Nature’s going to what it’s going to do. It’s great that there’s so much information out there about what you can do to protect yourself and your home, but it all boils down basically to ‘use your common sense.’”

___

Copyright 2012 The Associated Press.