Mid-coast residents will see tidal flooding, high winds and as much as 3 inches of rain through Tuesday as Hurricane Sandy makes landfall today in New Jersey in what forecasters are calling a “worst-case” storm.

State officials predict coastal flooding and beach erosion, and utility crews have been brought in from Canada to handle anticipated power failures.

For coastal Cumberland, Waldo and York counties and in Knox, Lincoln and Sagadahoc counties, the National Weather Service issued a Coastal Flood Warning, in effect today through 5 a.m. Tuesday.

Forecasters said the storm surge — ocean water pushed ashore by winds at high tide — could reach 4 feet. “Any flooding will be combined with strong wave action from high seas,” its advisory this morning said.

The best chance for flooding will be within a couple of hours either side of the high tides today and tonight. High tides today in Harpswell are expected at 11:30 a.m.; near noon on Tuesday.

“The combination of surge and high tides could bring the water level to about a foot or a foot and a half above flood level,” today’s advisory said. “However, combined with forecast high seas and strong wave action, this will lead to significant splash-over and beach erosion. Due to the height of the surge and the large waves expected, beach erosion may occur even in between the high tide cycles.”

A Coastal Flood Warning means that flooding is “occurring or imminent.”

A High Wind Warning is also in effect throughout much of the state today, with gusts expected to play havoc with utility lines. Tens of thousands of people are already without power this morning in Connecticut.

National Weather Service meteorologist Mike Kistner said winds will be picking up throughout today. Gov. Paul LePage issued a limited emergency declaration Friday, enabling utility workers from outside Maine to help restore power.

Kistner said a conservative estimate on rainfall was 1 to 3 inches for the state, with mountain areas seeing more rain.

“There will be some coastal flooding, but it doesn’t look like it will be significant,” said Kistner.

Gusts could top 70 mph along the coast, Kistner said.

“For a short period overnight, definitely 70 mph gusts won’t be out of the question for areas along the coast,” he said.

Schools are in session today across Mid-coast Maine, and businesses and governmment offices also are open as usual.

Dubbed “Frankenstorm,” Hurricane Sandy is bearing down on the Eastern Seaboard’s largest cities today, forcing the shutdown of mass transit, schools and financial markets in the nation’s most densely populated cities.

Sandy strengthened before dawn and stayed on a predicted path toward Washington, Baltimore, Philadelphia and New York — putting it on a collision course with two other weather systems that could create a superstorm with the potential to wreak havoc over 800 miles from the East Coast to the Great Lakes.

The tempest could endanger up to 50 million people for days.

In New York, many workers planned to stay home today as subways, buses and trains shut down across the region under the threat of flooding that could inundate tracks and tunnels. Airports also closed, and authorities warned that the time for evacuation was running out or already past. Utilities brought in extra crews, anticipating widespread power failures.

The center of the storm was positioned to come ashore tonight in New Jersey, meaning the worst of the surge could be in the northern New Jersey, New York City and Long Island. Higher tides brought by a full moon compounded the threat to a metropolitan area with about 20 million people.

“This is the worst-case scenario,” said Louis Uccellini, environmental prediction chief for the National Oceanic and Atmospheric Administration.

As rain from the leading edges began to fall over the Northeast on Sunday, hundreds of thousands of people from Maryland to Connecticut were ordered to leave lowlying coastal areas, including 375,000 in lower Manhattan and other parts of New York City, 50,000 in Delaware and 30,000 in Atlantic City, N.J., where the city’s 12 casinos shut down for only the fourth time ever.

“I think this one’s going to do us in,” said Mark Palazzolo, who boarded up his baitand tackle shop in Point Pleasant Beach, N.J., 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.’”

President Barack Obama declared emergencies in Massachusetts, Connecticut, Rhode Island, New York, New Jersey and Pennsylvania, authorizing federal relief work to begin well ahead of time. He 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,” Obama said. “We are not going to get bogged down with a lot of rules.”

Authorities warned that New York could get hit with a surge of seawater 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.

Major U.S. financial markets, including the New York Stock Exchange, Nasdaq and CME Group in Chicago, planned a rare shutdown today. The NYSE closed on Sept. 27, 1985, for Hurricane Gloria. The United Nations also shut down and canceled all meetings at its New York headquarters.

New York called off school today for the city’s 1.1 million students and announced it would suspend all train, bus and subway service Sunday night. More than 5 million riders a day depend on the transit system.

“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,” Mayor Michael Bloomberg warned. “This is a serious and dangerous storm.”

New Jersey Gov. Chris Christie was typically blunt: “Don’t be stupid. Get out.”

Wary of being seen as putting their political pursuits ahead of public safety, Obama and Republican nominee Mitt Romney reshuffled campaign plans as the storm approached.

In Virginia, one of the most competitive states, election officials eased absentee voting requirements for those affected by the storm. Early voting was canceled today in Maryland and the District of Columbia.

Sandy, a Category 1 hurricane with sustained winds of 85 mph early today, was blamed for 65 deaths in the Caribbean before it began traveling northward, parallel to the Eastern Seaboard. As of 5 a.m. today, it was centered about 385 miles southsoutheast of New York City, moving to the north at 15 mph, with hurricane-force winds extending an unusual 175 miles from its center.

Gale-force winds blew overnight over coastal North Carolina, southeastern Virginia, the Delmarva Peninsula and coastal New Jersey.

Sandy was expected to hook inland today, colliding with a wintry storm moving in from the west and cold air streaming down from the Arctic, and then cut across into Pennsylvania and travel up through New York state.