WTSP-TV, Tampa-St. Petersburg, Fla.

Tropical Storm Arthur has strengthened into a hurricane taking aim at North Carolina's Outer Banks, a thin ribbon of barrier islands and popular vacation spot, before the Fourth of July holiday, .

Dare County, N.C., officials said a mandatory evacuation of Hatteras Island along the Outer Banks would begin at 5 a.m. Thursday. After that time, no one will be allowed on the island.

A voluntary evacuation was announced earlier for the Outer Banks' Ocracoke Island, which is accessible only by ferry.

Officials told residents and out-of-town visitors who already may have arrived for the Fourth of July weekend to evacuate during daylight before the tropical storm brings high winds, rough seas, dangerous rip currents and possible flooding on North Carolina 12. The two-lane highway is the only way on and off the island other than ferries to the south, and twice in recent years, storm-driven waves have rendered the road impassable.

The National Hurricane Center has issued a hurricane warning for all of Dare County.

"I've been through Irene. I went through Isabelle," said Bill Motley, who works at Ace Hardware in Nags Head has lived on the Outer Banks for 13 years. "I'm not even worried about this one. I'm more worried about my tomato plants. With the wind coming, if we get a 50-mph gust, it will knock over my tomato plants."

Still, Gov. Pat McCrory declared a state of emergency for 25 coastal and adjoining counties.

"Don't put your stupid hat on," he said, as he urged surfers and swimmers not to get in the water regardless of how good the waves might be. "Our major goal is to ensure that no lives are lost during this upcoming storm."

The approaching storm was having an impact to the north as well. In Boston, the annual July 4th Boston Pops concert and fireworks display was advanced by a day to Thursday evening because of the threat of severe weather Friday from the storm.

The first named storm of the Atlantic hurricane season prompted a hurricane warning for a wide swath of the North Carolina coast and had officials, hotel owners and would-be vacationers as far north as New England carefully watching forecasts.

Arthur was about 160 miles south of Charleston — about 100 miles off the coast at the Florida-Georgia border — and moving north about 8 mph with maximum sustained winds of 70 mph late Wednesday. The National Hurricane Center predicted it would grow to a Category 1 hurricane with sustained winds of at least 74 mph sometime Thursday.

The forecast did not call for a landfall in the USA, but officials and travelers north to New England kept an eye on the storm's projected path. Many areas warned of upcoming rain, wind and potential rip tides.

Forecasters said Arthur was becoming better organized but is likely to stay just offshore, passing well to the east of northeastern Florida on Wednesday night and moving parallel to the southeastern U.S. coast, becoming a hurricane Thursday but losing much of its punch by Saturday morning.

The worst of the storm should occur at Cape Hatteras, N.C., about dawn Friday, with 3 to 5 inches of rain and sustained winds up to 85 mph, said Tony Saavedra, a meteorologist at the National Weather Service. The storm should move through quickly and be off the coast of New England later in the day, perhaps making landfall in Canada's maritime provinces as a tropical storm.

The center's experimental storm surge map shows the potential for up to 3 feet of flooding in many areas of northwest Florida and Georgia east of Interstate 95. From the Wilmington, N.C. area along the fragile barrier islands, storm surges could be as much as 6 feet in some areas.

In the Myrtle Beach area, the heart of South Carolina's $18 billion tourism industry, Arthur was expected to move in by Thursday night, spinning wind gusts from 40 to 50 mph toward the high-rise hotels and condominiums lining the oceanfront.

Farther south, in Hilton Head Island on the state's southern tip, most were confident the storm would pass well out at sea.

"It will be a sold-out weekend," said Charlie Clark, a spokeswoman for the local Chamber of Commerce. "We're not getting calls from visitors asking what's up with this storm."

Contributing: William M. Welch, USA TODAY; The Associated Press, Florida Today and The Fort Myers (Fla.) News-Press

2014 Atlantic hurricane season names

The National Hurricane Center, which has been naming Atlantic tropical storms since 1953, has created a list of 21 names per year through 2019. Here are this year's names:

• Arthur

• Bertha

• Cristobal

• Dolly

• Edouard

• Fay

• Gonzalo

• Hanna

• Isaias

• Josephine

• Kyle

• Laura

• Marco

• Nana

• Omar

• Paulette

• Rene

• Sally

• Teddy

• Vicky

• Wilfred

Source: National Hurricane Center