Hurricane Irene began lashing the east coast with rain with the potential to cause billions of dollars in damage along a densely populated arc that included Washington, Baltimore, Philadelphia, New York and Boston. At least 65 million people could be affected.
President Obama said all indications point to the storm being a historic hurricane.
"I cannot stress this highly enough. If you are in the projected path of this hurricane, you have to take precautions now," Obama said Friday from Martha's Vineyard, where he was wrapping up a vacation.
The president was to return to the White House on Saturday, the same day the storm is expected to pass through the area around the nation's capital.
As Irene trudged northwest from the Bahamas, rain from its outer bands began falling along the North and South Carolina coast.
Capt. Stephen Russell, head of the Bahamas National Emergency Management Agency, said the storm knocked out communications to islands such as Eleuthera and Abaco and that the government has only partial reports of damage to houses and flooding. Russell said on state-owned ZTV that there have so far been no reports of deaths or injuries anywhere in the Bahamas, but 70 homes on the southern island of Acklins were destroyed, 29 sustained major damage and 84 received minor damage.
The capital sustained relatively minor flooding and damage. Irene was expected to be completely out of Bahamian territory later Friday.
In the Carolinas, swells and waves up to 9 feet (3 meters) were reported along the Outer Banks. Winds were expected to pick up later. Thousands had already lost power as the fringes of the storm began raking the shore.
Hurricane warnings remained in effect from North Carolina to New Jersey. Hurricane watches were in effect even farther north and included Long Island, Martha's Vineyard and Nantucket, Massachusetts.
Risks from Irene's wrath were many: surging seas, drenching rains, flash floods and high winds. The head of the Federal Emergency Management Agency had warned previously that this is one of the largest populations to be affected by one storm at one time.
In addition to widespread wind and water damage, Irene could also push crude oil prices higher if it disrupts refineries in Delaware, New Jersey, Pennsylvania and Virginia, which produce nearly 8 percent of U.S. gasoline and diesel fuel.
By late Friday morning, Irene remained a Category 2 storm with maximum sustained winds near 105 mph (169 kph). Little change in strength was expected by the time Irene reaches the North Carolina coast on Saturday, but forecasters at the National Hurricane Center warned it would be a large and dangerous storm nonetheless.
The hurricane could be the strongest to strike the East Coast in seven years, and people were already getting out of the way. Irene already had pummeled the Caribbean, causing floods and power outages.
The center of the storm was still about 330 miles (531 kilometers) south-southwest of Cape Hatteras, North Carolina, and moving to the north at 14 mph (22 kph).
The latest forecasts showed Irene crashing into the North Carolina coastline Saturday, then churning up the Eastern Seaboard and drenching areas from Virginia to New York City before a weakened storm reaches New England.
In Washington, Irene dashed hopes of dedicating a 30-foot (10-meter) sculpture to Martin Luther King Jr. on Sunday on the National Mall. While a direct strike on the nation's capital appeared slim, organizers said the forecasts of wind and heavy rain made it too dangerous to summon a throng they expected to number up to 250,000.
Hundreds of thousands of New Yorkers were told Thursday to pack a bag and be prepared to move elsewhere. The nation's biggest city has not seen a hurricane in decades, and a hurricane warning hasn't been issued there since Hurricane Gloria hit in 1985 as a Category 2 storm, said Ashley Sears, a meteorologist with the National Weather Service.
Even if the winds aren't strong enough to damage buildings in a metropolis made largely of brick, concrete and steel, a lot of New York's subways and other infrastructure are underground, making them subject to flooding.
New York's two airports are close to the water and could be inundated, as could densely packed neighborhoods, if the storm pushes ocean water into the city's waterways, officials said. In 2008, the city had a brush with Tropical Storm Hanna, which dumped 3 inches of rain on Manhattan.
In the last 200 years, New York has seen only a few significant hurricanes. In September 1821, a hurricane raised tides by 13 feet in an hour and flooded all of Manhattan south of Canal Street, the southernmost tip of the city. The area now includes Wall Street and the World Trade Center memorial.
An infamous 1938 storm dubbed the Long Island Express came ashore about 75 miles east of the city and then hit New England, killing 700 people and leaving 63,000 homeless.
The first US injuries from Irene appeared to be in South Florida near West Palm Beach, where eight people were washed off a jetty Thursday by a large wave churned up by the storm.