(CNN) -- Hurricane Sandy's outer bands pummeled the East Coast on Monday with howling winds, torrential downpours and storm surges that authorities warned could bring widespread devastation.
"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.
The storm's center was expected to make landfall by early evening along or just south of the southern New Jersey coast.
An expected storm surge at midnight could raise water levels to 11 feet above normal high tide, bringing "the potential to cause unprecedented damage."
By Monday afternoon, more than 765,000 electric customers in seven states had already lost power.
Hundreds of thousands of people had abandoned their homes and apartments. New York City landmarks were eerily empty. The nation's capital was emptied of government workers.
Forecasters said Sandy's collision with a cold front once it makes landfall could create a "superstorm" that could generate flash floods, snowstorms and 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 the presidential 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 Monday from Florida to Washington, where he told reporters at the White House that assets were in place for an effective response.
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.
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.
Hurricane-force winds extended outward 175 miles from the storm's center, and tropical storm-force winds reached 485 miles.
Gale-force winds were blowing from North Carolina 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.
Sandy is likely to set a record as the strongest storm to make landfall north of Cape Hatteras, North Carolina, since recordkeeping began, 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 was expected to move slowly northward, meaning gusty winds and heavy rain (and snow on the western side of the storm) would continue through Wednesday.
Tropical storm-force winds were expected to stretch from Cape Hatteras to Canada.
Hurricane-force gusts were possible from south of Philadelphia northward into New York City. These gusts could extend more than 200 miles inland.
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.
Far above West 57th Street, a crane snapped and dangled from the side of a luxury high-rise under construction; police closed part of the street.
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.
Atlantic City was forecasting a storm surge of 9.5 feet, another record. 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.
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. Twelve to 18 inches of snow were expected in the mountains near the North Carolina-Tennessee border.
New York halted 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.
Other mass transit systems suspended services Monday, including Washington's Metro service and Southeastern Pennsylvania Transportation Authority trains and buses in and around Philadelphia.
Amtrak canceled service through Tuesday along in the Northeast.
Thousands of flights have been canceled, and hundreds of roads and highways were expected to flood.
"This is not a typical storm," said Pennsylvania Gov. Tom Corbett. "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, but Cafaro was not optimistic that Sea Bright would be spared Sandy.
Meteorological data supported her view: Hours before landfall, storm surge for Sandy was higher than it had been for Irene after landfall.
"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."
Officials canceled classes Monday for more than 2 million public school students in 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 ordered closed Monday and Tuesday -- the first such closure for weather since 1985, when Hurricane Gloria struck.
CNN's Greg Botelho, Michael Holmes, Jareen Iman, Alison Kosik, Sarah Dillingham, Brandon Miller, George Howell, Athena Jones, Shawn Nottingham and Devon Sayers contributed to this report.