BUXTON, N.C. — A nightmare Hurricane Irene barreled toward the Eastern Seaboard on Thursday, sending thousands of vacationers fleeing and threatening up to 65 million people from the Carolinas to New England.

The Category 3 storm with winds of 115 mph — the threshold for a major hurricane — would be the strongest to strike the East Coast in seven years, and people were already getting out of the way.

Tens of thousands fled North Carolina beach towns, farmers pulled up their crops, and the Navy ordered ships to sea so they could endure the punishing wind and waves in open water.

All eyes were on Irene’s projected path, which showed it bringing misery to every city along the I-95 corridor, including Washington, New York and Boston. The former chief of the National Hurricane Center called it one of his three worst possible situations.

“One of my greatest nightmares was having a major hurricane go up the whole Northeast Coast,” Max Mayfield, the center’s retired director, told The Associated Press.

The governors of North Carolina, Virginia, Maryland, New York and New Jersey declared emergencies to free up resources, and authorities all the way to New England urged residents in low-lying areas to gather supplies and learn the way to a safe location.

Irene was expected to come ashore Saturday in North Carolina with 115 mph winds and a storm surge of 5 to 10 feet. It could dump a foot of rain, with as much as 15 inches falling in some places along the coast and around Chesapeake Bay.

Scientists predict Irene will then chug up the coast. Some forecasts showed it taking dead aim at New York City, with its eye passing over Brooklyn and Manhattan before weakening and trudging through New England.

Printed on Friday, August 26, 2011 as: Northeast coast prepares for Category 3 hurricane.