Forecasters and emergency management officials were urging beachgoers to use caution when going into the surf.
NOAA, National Weather Service
"People look at the skinny black (forecast) line and say 'That's 100 miles (160 km) east, I'm not going to get that storm,'" hurricane center spokesman Dennis Feltgen said.
But he warned, "The impacts of the storm could be over a much wider area."
Low wind shear conditions and warm sea-surface temperatures should allow for steady strengthening, the NHC forecast said. Arthur is expected to become a hurricane by Friday morning, reaching a maximum of 80 mph (128 kph) winds, before losing strength.
The storm was located on Tuesday about 95 miles (155 km) southeast of Cape Canaveral, Florida, and about 80 miles (130 km) north to northwest of Freeport, Grand Bahama Island, with maximum sustained winds of 40 miles per hour (64 kph).
Moving toward the northwest at nearly 2 mph (3.2 kph), it was forecast to remain offshore and move east of the east-central coast of Florida during the next day or so, the NHC said.
The storm will have the heaviest impact on coastal areas from North Carolina to Cape Cod, Massachusetts, and Long Island, New York, according to meteorologists at AccuWeather.com.
It is too early to tell how close to the coast of North Carolina the storm will get, Feltgen said. Emergency management officials in the state said they were making preparations.