(Reuters) - Gasoline prices in the United States rose nearly 8 cents a gallon over the past two weeks largely because Hurricane Issac forced temporary reductions in refining capacity, according to a widely-followed survey.

The national average price of a gallon of regular gas was $3.838 on September 7, up from $3.759 on August 24, said Trilby Lundberg, editor of the Lundberg Survey, which covers some 2,500 gas stations nationwide.

The hurricane, which passed across the Gulf of Mexico at the end of August, caused some refineries to shut down and others to reduce their capacity, she said.

Less than a penny of the nearly 8-cent rise was due to higher prices for crude oil, Lundberg said.

"We probably will not see further price hikes in the next two weeks," said Lundberg. Capacity curtailed by the storm has come back, though the industry is limiting other facilities to perform maintenance and make upgrades.

The average price found in the survey was 13 cents a gallon lower than this year's high of $3.967, registered on April 6. The record high of $4.112 was set on July 11, 2008.

(Reporting by David Henry in New York; Editing by Diane Craft)