Hurricane warnings are in effect for coastal North Carolina, and the storm could pack 85 mph winds by the time its outer bands reach land early Friday. Arthur had 80 mph winds and was 300 miles southwest of Cape Hatteras as of 8 a.m. Thursday.
Authorities had on Wednesday begun closing campgrounds, lighthouses and beaches on the Outer Banks of North Carolina. Several towns and villages rescheduled Independence Day festivities and fireworks plans as the storm picked up speed.
North Carolina Gov. Pat McCrory declared a state of emergency on Wednesday for 25 eastern counties to help prepare for possible damage.
In Maryland, the only signs of Arthur on Friday could be dangerous surf and rip currents and blustery conditions. The storm was also expected to add moisture to an already hot and humid air mass, helping to fuel thunderstorms forecast late Thursday into Friday.
Ocean City officials rescheduled a fireworks display that had been planned for Friday night, citing difficulties setting up for the show. The celebration will be held Saturday night, instead.
The National Hurricane Center said areas along the East Coast should monitor Arthur's progress, but that the biggest risks of impacts from the storm are in southeastern New England.
While Arthur is the latest first tropical storm of any season since 2004, it is the earliest storm to reach hurricane status in two years.
Tropical Storm Alex, which eventually became Hurricane Alex, did not become a tropical storm until Aug. 1, 2004.
In 2012, Tropical Storm Chris reached hurricane status June 21.
Reuters contributed to this article.