Hurricane Earl has weakened to a Category 2 storm as it blows toward North Carolina's coast.

The storm had maximum sustained winds of 165 km/h, with additional weakening expected Friday, the U.S. National Hurricane Center said.

But the agency warned that Earl is expected to remain a large and strong hurricane as it passes near the Outer Banks of North Carolina.

The centre of the storm passed just east of the Outer Banks, the islands on North Carolina's coast, late Thursday night. Gusts above 65 km/h made signs shake and heavy rain fall sideways in Buxton, at the southeasternmost tip of the Outer Banks.

National Weather Service meteorologist Hal Austin told The Associated Press that the eye of the hurricane was expected to get as close as 88 kilometres east of the Outer Banks by about 2 a.m. Friday.

The centre of the storm is expected to approach southeastern New England on Friday night.

The coast is expected to be lashed by winds of hurricane strength for a couple of hours.

Earlier Thursday, North Carolina Gov. Bev Perdue warned that Hurricane Earl is a "serious storm" and people in North Carolina should brace for it.

Hurricane warnings, already in effect in parts of North Carolina, were also issued for portions of Massachusetts, forecasters said.

North Carolina, Virginia and Maryland have all signed orders declaring states of emergency, and mandatory evacuation orders are in effect for parts of coastal North Carolina.

Perdue urged people to pay attention to the forecasts and called on boaters to get out of the water.

"This is weather that's not in our control," Perdue said Thursday morning. "Right now it's still predicted just to brush the coast at the Outer Banks today, but again, nobody knows."

"It's a serious storm, and we all need to treat it like a serious storm," she said.

CBC meteorologist Johanna Wagstaffe said people would be able to feel tropical storm-force winds more than 200 kilometres from the centre of the storm.

Officials in coastal areas warned residents to brace for strong winds, heavy rain and large swells that could create rip currents.

Visitors to North Carolina's Ocracoke Island left the area on ferries Wednesday and people on Cape Hatteras were also told to leave. Both are part of the Outer Banks, with long stretches of sandy beaches popular with vacationers.

While thousands of tourists heeded calls to evacuate Hatteras Island, locals familiar with hurricanes vowed to ride out the hurricane, preparing to spend days stranded from the mainland.

"I worry about not being able to get back here,"' said Nancy Scarborough, who manages the Hatteras Cabanas. "I'd rather be stuck on this side than that side."

Town workers, from left, Jose Pineda, Travis Thompson, and Cager Jones, install barriers on the boardwalk as Hurricane Earl heads toward the eastern coast in Atlantic Beach, N.C., on Thursday. (Chuck Burton/Associated Press)

The North Carolina National Guard is deploying 80 troops to help and U.S. President Barack Obama declared an emergency in the state. The declaration authorizes the Department of Homeland Security and Federal Emergency Management Agency to co-ordinate all disaster relief efforts.

Farther up the East Coast, emergency officials urged people to have disaster plans and supplies ready and weighed whether to order evacuations as they watched the latest maps.

Residents in the Maritime provinces were also urged to prepare for the storm.

Environment Canada has issued a tropical storm watch for the Nova Scotia counties of Yarmouth, Shelburne and Queens.

Chris Fogarty, program supervisor for the Canadian Hurricane Centre, said the storm watch could be upgraded to a hurricane watch as the storm approaches.

Earl is expected to arrive in the Maritimes early Saturday, but it's still too early to know exactly when or where, forecasters said.

"We're definitely dealing with that range of uncertainty," said Fogarty.

With files from The Associated Press