(CNN) -- Hurricane Sandy's outer bands pummeled the Eastern Coast on Monday with howling winds, torrential downpours and storm surges that authorities warned could bring devastation unlike anything anyone has seen.
"This is the most catastrophic event that we have faced and been able to plan for in any of our lifetimes," Connecticut Gov. Dan Malloy said.
An expected storm surge at midnight could raise water levels to 11 feet above normal high tide, bringing "the potential to cause unprecedented damage."
Look at images of the storm in our Hurricane Sandy photo gallery online. Mobile users should click this link - http://bit.ly/sandyphotos
As of Monday afternoon, storm-related power outages numbered 300,000 customers in seven states.
Hundreds of thousands of people have abandoned their homes. New York City landmarks are eerily empty. The nation's capital is emptied of government workers.
Forecasters said Sandy was likely to collide with a cold front and spawn a "superstorm" that could generate flash floods, snowstorms and massive power outages from North Carolina to Maine.
The National Grid, which provides power to millions of customers, said 60 million people could be affected.
"It could be bad," said U.S. Coast Guard Rear Adm. Steven Rattior, "or it could be devastation."
The predicted impact extends beyond the East Coast. Wave heights in Lake Michigan could reach 28 feet Monday night and 31 feet by Tuesday, the National Weather Service said.
Eight days before Election Day, with both candidates locked in a tight race, President Barack Obama and his Republican challenger, Mitt Romney, altered or canceled planned campaign events because of the storm.
Obama returned to Washington on Monday from Florida and went directly to a White House Situation Room briefing on the storm. He then told reporters that he was confident that assets had been positioned for an effective response to the aftermath of the storm.
He urged those in the path of the storm to heed warnings and other instructions.
"The most important message I have for the public right now is please listen to what your state and local officials are saying," Obama said. "When they tell you to evacuate, you need to evacuate."
Obama said he was not worried about how the storm might affect the election. "I'm worried about the impact on families; I'm worried about the impact on first responders; I'm worried about the economy and transportation," he told reporters. "The election will take care of itself next week."
In Avon Lake, Ohio, Romney asked supporters to drop off items and cash at his "victory centers" to be donated to victims of the storm.
"There are families in harm's way that will be hurt -- either in their possessions or perhaps in something more severe," Romney said.
The campaign canceled events that had been planned for later in the day and Tuesday for Romney and his running mate, Rep. Paul Ryan.
Sandy claimed at least 67 lives -- 51 in Haiti -- on its path last week across the Caribbean.
Early Monday, Sandy started to turn toward the United States. At 2 p.m., the Category 1 hurricane was 110 miles southeast of Atlantic City, New Jersey, and 175 miles south-southeast of New York City, the National Hurricane Center said. Maximum sustained winds were 90 mph, and Sandy was moving north-northwest at nearly 28 mph, up from 18 mph three hours before.
The center was expected to make landfall by early evening along or just south of the southern New Jersey coast.
Hurricane-force winds extended outward 175 miles from the storm's center, and tropical storm-force winds reached 485 miles.
Gale-force winds were already occurring over parts of the Mid-Atlantic states -- from North Carolina up to New York's Long Island. The winds were expected to spread later in the day over more of the coast, New York City and southern New England.
Based on pressure readings, Sandy is likely to be the strongest storm to make landfall north of Cape Hatteras, North Carolina, said CNN senior meteorologist Dave Hennen. The benchmark storm, the 1938 "Long Island Express" Hurricane, contained a low pressure reading of 946 millibars. Sandy had a minimum pressure of 943 millibars. Generally speaking, the lower the pressure, the stronger the storm.
The area of tropical storm-force winds extended nearly 1,000 miles -- twice the size of Texas. If it were a country, it would be the world's 20th-largest.
According to a government model, Sandy's wind damage alone could cause more than $7 billion in economic loss.
By Monday afternoon, 23 states were under a warning or advisory for wind related to Sandy.
The storm was expected to weaken once it moves inland, but the center will move slowly northward, meaning gusty winds and heavy rain (and snow on the western side of the storm) will continue through Wednesday.
Tropical storm-force winds were expected to stretch from Cape Hatteras to Canada.
Hurricane-force gusts were possible from
High-rise buildings are particularly vulnerable as winds increase with height. For example, in New York, winds Monday night could gust to 80 mph. At a 30-story level, these winds would be near 100 mph.
A storm surge of 10 to 12 feet was predicted for Lower Manhattan's Battery Park, which could break the 1960 record of 10.5 feet set by Hurricane Donna. It could lead to catastrophic flooding.
Atlantic City was forecasting a storm surge of 9.5 feet, another record. Rains were already blanketing much of the Mid-Atlantic to Northeast. Atlantic City authorities ordered a curfew from 6 p.m. Monday to 6 a.m. Tuesday police said.
Storm surge -- the combination of a storm and a high tide -- "will cause normally dry areas near the coast to be flooded," the weather service said. It said water depths could reach 6 to 11 feet along Long Island Sound and New York Harbor.
"Elevated waters could occur far removed from the center of Sandy," it added.
Three to six inches of rain were expected over far northeastern North Carolina, with isolated maximum totals of eight inches possible, it said.
Four to eight inches of rain were expected over portions of the Mid-Atlantic states, with isolated amounts of 12 inches possible.
Two to three feet of snow were likely to accumulate in the mountains of West Virginia and one to two feet in the mountains of southwestern Virginia to the border with Kentucky. One to 1½ feet of snow were expected in the mountains near the North Carolina-Tennessee border.
By early Monday, New York, the city that never sleeps, bedded down after halting service on its bus and train lines, closing schools and ordering about 400,000 people out of their homes in low-lying areas of Manhattan and elsewhere.
Amtrak canceled service through Tuesday.
The process of halting subway service in New York began Sunday night. Other mass transit systems suspended services Monday, including Washington's Metro service and Southeastern Pennsylvania Transportation Authority trains and buses in and around Philadelphia.
Thousands of flights have been canceled, and hundreds of roads and highways expected to flood.
"This is not a typical storm. It could very well be historic in nature and in scope and in magnitude because of the widespread anticipated power outages, flooding and potential major wind damage," Pennsylvania Gov. Tom Corbett said.
"Essentially, this is a hurricane wrapped in a 'nor'easter."
In Sea Bright, New Jersey, Yvette Cafaro scrawled a plea on the plywood that covered her burger restaurant: "Be kind to us Sandy."
The seaside area largely dodged last year's Hurricane Irene, and Cafaro is hoping for another reprieve, but not optimistic.
"Everything that we've been watching on the news looks like this one will really get us," she said. "We're definitely worried about it."
After filling his trunk with sandbags Sunday in Cranston, Rhode Island, resident Steve Pacheco said he had done what he could by clearing Halloween decorations and other items from his yard. Still, he said, he was nervous.
"I don't want to go through this again," Pacheco told CNN affiliate WPRI-TV in Providence.
Officials canceled classes Monday for more than 2 million public school students in districts such as New York, Philadelphia, Boston and Baltimore, while universities and federal offices in Washington and government offices in states such as New Jersey were closed.
The New York Stock Exchange was closed Monday and will remain closed Tuesday. The last time it closed for a weather event was in 1985, during Hurricane Gloria.
Politicos said it was unclear what effect the storm would have on the presidential race, though access to voting centers would be a concern if the storm's effects persist.
"I don't think anybody really knows," top Obama adviser David Axelrod said Sunday on CNN's "State of the Union."
"Obviously, we want unfettered access to the polls because we believe that the more people come out, the better we're going to do, and so, to the extent that it makes it harder, you know, that's a source of concern."
Virginia's Republican governor said Sunday that his state would take measures to ensure residents are able to vote despite obstacles the storm might bring. Virginia is one of a handful of battleground states.