(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