Hurricane Earl has strengthened again to a Category 4 hurricane as it continues its path toward the U.S. East Coast.

The storm had top sustained winds of 220 km/hr as it threatened to bring heavy winds, rain and high waves and force thousands of tourists from two vacation islands in North Carolina.

The governors of North Carolina, Virginia and Maryland declared a state of emergency.

U.S. National Hurricane Center issued a hurricane warning at 11 a.m. ET that extended northward into Cape Henlopen, Del. An earlier warning had extended only from Bogue Inlet, N.C., to the North Carolina-Virginia border.

Cars head north on Highway 12 in Avon, N.C., fleeing Hurricane's Earl anticipated arrival, on Wednesday. (Gerry Broome/Associated Press)Forecasters predicted the core of the hurricane would pass east and northeast of the Bahamas on Wednesday.

As of 2 p.m. ET, Earl was churning 440 kilometres east of Abaco Island in the Bahamas and travelling at approximately 28 kilometres an hour.

It was expected to reach the North Carolina coast late Thursday and wheel to the northeast, staying offshore while making its way up the Eastern Seaboard.

But forecasters said it could move in closer, perhaps coming ashore in North Carolina, crossing New York's Long Island and passing over the Boston metropolitan area and Cape Cod.

That could make the difference between modestly wet and blustery weather on the one hand and a dangerous storm surge, heavy rain and hurricane-force winds on the other.

The storm could make landfall anywhere between Maine and Cape Breton, N.S., the Canadian Hurricane Centre said.

N.C. tourists leave

Visitors to North Carolina's Ocracoke Island left the area on ferries and those visiting Cape Hatteras were also told to leave. Both are part of the Outer Banks, a chain of barrier islands along the state's coast with long stretches of sandy beaches popular with vacationers.

Hyde County emergency officials asked 5,000 visitors to begin leaving Ocracoke Island at 5 a.m. ET Wednesday.

The order is not compulsory, but emergency services director Lindsey Mooney said officials hope the island's roughly 800 year-round residents will follow tourists to shore.

Federal authorities also warned people on the coast to be prepared to evacuate if necessary.

"A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm force winds," the U.S. hurricane centre said in a statement. Preparations to protect people and property should be "rushed to completion" when a warning is issued, the centre said.

Impacts on Atlantic Canada

CBC meteorologist Johanna Wagstaffe said it is still too early to tell the exact impact Hurricane Earl may have on Atlantic Canada.

"But forecasters are fairly confident that it will still be a hurricane when it reaches Canadian waters for the weekend," she said.

The Canadian Hurricane Centre is urging people in the Atlantic region to pay very close attention to weekend weather forecasts as the storm approaches.

With files from The Associated Press and The Canadian Press