The concert, which ends with Tchaikovsky's "1812 Overture" and a fireworks show, draws as many as 1 million people to the Esplanade along the Charles River every year. State Police Col. Timothy Alben announced the change in plans at a news conference Wednesday.
"We are struggling with models and projections and possibilities and so forth," Alben said. "We've got to be somewhat flexible here."
The orchestra was already scheduled to hold an open rehearsal Thursday night with an expected audience of about 75,000.
Arthur, the first named storm of the 2014 Atlantic hurricane season, is expected to become a hurricane Thursday. The National Hurricane Center in Miami predicted the storm will be off the Outer Banks of North Carolina by Friday morning, heading northeast.
While Arthur is not expected to hit the coast full force, officials in the mid-Atlantic and New England states were preparing for a holiday weekend of heavy rain and rough surf.
State Fire Marshal Stephen Coan warned local officials in Massachusetts that fireworks displays should not be held during rainstorms or in high wind and warned that surf could make barge-based fireworks dangerous. Some towns had already announced changes in schedule.