Tropical Storm Arthur formed off the Florida coast and is forecast to grow into a hurricane that will threaten North Carolina's Outer Banks during the Fourth of July holiday.
The storm was 95 miles (153 kilometers) southeast of Cape Canaveral, Florida, with maximum winds of 40 mph as of 11 a.m. local time, the National Hurricane Center said in an advisory. Tropical storm watches were posted for Florida's eastern coast from Fort Pierce to Flagler Beach.
"For vacationers going out there to the Outer Banks, they will have some concerns and will have to watch this," said Paul Walker, a meteorologist with AccuWeather in State College, Pennsylvania. "It could strengthen to a hurricane and then pass through or near the Outer Banks Thursday night into Friday."
Arthur is the first named system of the 2014 Atlantic hurricane season, which runs from June 1 through Nov. 30. Arthur's winds are expected to peak at 80 mph, making it a Category 1 storm on the five-step Saffir-Simpson hurricane scale, in the next three days.
The Outer Banks have more than a 60 percent chance of being struck by winds of at least 39 mph as the storm approaches, the hurricane center said.
"Low shear conditions and warm sea-surface temperatures should allow for at least steady strengthening," Stacy Stewart, a senior hurricane specialist at the center in Miami, said in an analysis.
One to 3 inches (2.5 to 8 centimeters) of rain are expected to fall across central Florida, while parts of the Bahamas may get as much as 6 inches before the system tracks north, the hurricane center said.
Florida Power & Light, the state's largest utility and a unit of NextEra Energy, has spent $1.5 billion to strengthen its grid against storms since two hurricanes struck in 2004, Bill Orlove, a spokesman, said in a telephone interview. Hurricanes Charley and Frances combined that year to cause $15 billion in damage in the U.S., mostly in Florida, according to the National Oceanic and Atmospheric Administration.
After Arthur passes the Outer Banks, it will move northeast during the day on July 4, blocking a cold front coming across the U.S. That means Boston should receive some heavy rain, said Rob Carolan, owner of Hometown Forecast Services in Nashua, New Hampshire.
Carolan said most of the rain from the front will probably miss New York City, where the Fourth of July may start cloudy and then clear by nightfall. Any areas behind the frontal boundary, such as the vacation spots of northern New England, should also be clear.
"Anyone back behind the front will have a glorious weekend," Carolan said.