RALEIGH, N.C. — Powerful Hurricane Earl spun toward the East Coast on Wednesday, driving tourists from North Carolina’s vacation islands and threatening to bring damaging winds and waves to the Atlantic seaboard through Labor Day weekend.

North Carolina Gov. Beverly Perdue and Maryland Gov. Martin O’Malley declared states of emergency and federal authorities have warned people along the coast to be prepared to evacuate if necessary.

The evacuation of the Outer Banks, a stretch of thin barrier islands, had begun in North Carolina and hundreds of cars were backed up on a highway that is the sole link to the mainland. Earl’s strongest winds were expected to reach the coast Thursday night into Friday morning.

Earl’s effect on the East Coast will depend on when it makes its expected turn to the northeast.

A later-than-expected turn could mean the storm’s eye makes landfall on the extreme eastern tip of North Carolina as a Category 3 storm late Thursday or early Friday.

If that happens, hurricane-force winds also could reach New York’s Long Island and Cape Cod in Massachusetts.

Even if it doesn’t, dangerous rip currents likely to be felt from the Carolinas north.

Virginia’s Gov. Bob McDonnell declared a state of emergency as a precaution, allowing the state to position staff and resources ahead of the storm. Emergency officials as far north as Maine urged people to have disaster plans and supplies ready.

Even the U.S. Navy was altering plans, hustling to get the USS Cole back in port in Norfolk, Va., before the bad weather arrived. The destroyer wasn’t supposed to come home from a seven-month deployment until later this week.

In Virginia Beach, where more than 20,000 long-distance runners, their families and friends are due to arrive this weekend for the Dodge Rock ’n’ Roll Virginia Beach Half Marathon, organizers were keeping a close eye on the weather, but few participants had backed out.

“This is definitely on our radar, but at this time it looks like Sunday’s half-marathon will take place as scheduled,” said Dan Cruz.

Earl was still more than 680 miles south-southeast of Cape Hatteras on Wednesday afternoon, with top sustained winds of 125 mph. Forecasters said Earl is strengthening and could become a Category 4 storm later Wednesday with winds of 131 mph or greater.

It was on track to near the North Carolina shore late Thursday or early Friday and then blow north along the coast, with forecasters cautioning that it was still too early to tell how close the storm may come to land.

The National Weather Service issued a hurricane warning for much of the North Carolina coast and hurricane watches from Virginia to Delaware.

Not since Hurricane Bob in 1991 has such a powerful storm had such a large swath of the East Coast in its sights, said Dennis Feltgen, spokesman for the National Hurricane Center.

“A slight shift of that track to the west is going to impact a great deal of real estate with potential hurricane-force winds,” Feltgen said.

The only evacuation orders so far affected parts of the Outer Banks, thin strips of beach and land that face the open Atlantic.

Tourist cars, some with campers in tow, lined up for the first ferries of the day from Ocracoke to the mainland. Another car ferry connects to Hatteras, which has a bridge to the mainland and came under the second evacuation order a little later Wednesday morning.

The evacuation orders are called mandatory, but Julia Jarema, spokeswoman for the state Division of Emergency Management, said it doesn’t mean people will be forced from their homes. Local law enforcement officials may do something such as going door-to-door and asking people who stay behind for information about their next of kin.

Emergency officials said they hoped Ocracoke’s 800 or so year-round residents would heed the call to leave. But Carol Pahl said she and husband Tom would stay put if the current forecasts hold. Only a direct hit from a stronger storm would drive them from the island where they’ve lived for seven years, running an antiques store.

“There’s never been a death on Ocracoke from a hurricane, so we feel pretty comfortable,” Carol Pahl said as tourists departed on ferries and her husband, also a construction contractor, worked to board up the windows of clients’ and friends’ homes. “Everything here is made pretty much with hurricanes in mind.”