Updated at 4:29 p.m. ET
NAGS HEAD, N.C. - Hurricane Irene began lashing the East Coast with fierce winds and rain Friday, with the storm almost certain to heap punishment on a vast and densely populated stretch of shoreline from the Carolinas to Massachusetts this weekend.
Rain and tropical storm-force winds of at least 39 mph already were pelting the Carolinas as Irene trudged north, snapping power lines and flooding streets. Officials warned of dangerous rip currents as Irene roiled the surf. Thousands already were without power. In Charleston, S.C., several people had to be rescued after a tree fell on their car, trapping them.
For hundreds of miles, people in the storm's path either fled inland or stocked up on supplies to ride it out. Irene had the potential to cause billions of dollars in damage and affect some 65 million people in cities including Washington, Baltimore, Philadelphia, New York and beyond.
Officials along the entire Eastern Seaboard declared emergencies, shut down public transit systems and begged residents to obey evacuation orders ahead of the storm, which federal officials said is likely to affect more people than many others before it.
President Obama said all indications point to the storm being historic.
"I cannot stress this highly enough. If you are in the projected path of this hurricane, you have to take precautions now," said Mr. Obama, who was wrapping up his Martha's Vineyard vacation a day early and heading back to the White House on Friday.
Irene's wrath in the Caribbean, including Puerto Rico, the Dominican Republic and the Bahamas, gave a preview of what is expected in the U.S.: Power outages, dangerous floods and high winds that caused millions of dollars in damage.
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, Mass.
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 Friday afternoon, Irene had weakened slightly but remained a Category 2 storm with maximum sustained winds near 100 mph. Little change in strength was expected by the time Irene reaches North Carolina on Saturday, but forecasters at the National Hurricane Center warned it would be a large and dangerous storm nonetheless.
In North Carolina, traffic was steady Friday as people fled the Outer Banks and beach towns. Tourists had been ordered to leave the barrier islands, though local officials estimated Friday that about half the residents on two of the islands have ignored evacuation orders.
In Nags Head, police officer Edward Mann cruised the streets in search of cars in driveways a telltale sign they planned to stay behind. He warned those that authorities wouldn't be able to help holdouts in hurricane-force winds, and that electricity and water could be out for days.
Some tell Mann they're staying because they feel safe or because the storm won't be as bad as predicted. Mann, 25, said some have told him they've ridden out more storms than years he's been alive.
Bucky Domanski, 71, was among those who told Mann he wasn't leaving. The officer handed the retired salesman a piece of paper warning of the perils of staying behind. Domanski said he understood.
"I could be wrong, but everything meteorologists have predicted never pans out," Domanski said. "I don't know, maybe I've been lulled to sleep. But my gut tells me it's not going to be as bad as predicted. I hope I'm right."
"You can't count on that. Folks need to decide that they need to get out now," she said.
Most tourists have already gone, a huge help in keeping roads clear and traffic moving, CBS News Correspondent Mark Strassmann reports.
"So far people have been complying," Duck, N.C., police officer Tara Pouten tells Strassmann, "but residents staying could be a problem."
North Carolina was just first in line along the Eastern Seaboard home to some of the nation's priciest real estate.
Besides major cities, sprawling suburbs, ports, airports, highways, cropland and mile after mile of built-up beachfront neighborhoods are in harm's way. In several spots along the coast, hospitals and nursing homes worked to move patients and residents away from what could be the strongest hurricane to hit the East Coast in seven years.