Gasoline prices that reached all-time highs in the wake of Hurricane Katrina (search) fell by an average of 20 cents a gallon in the past two weeks as some Gulf Coast refineries resumed production, according to the Lundberg Survey (search).

The weighted average price for all three grades of gasoline was $2.84 a gallon on Sept. 23, said Trilby Lundberg, who publishes the semimonthly Lundberg Survey of 7,000 gas stations. Self-serve regular averaged $2.81 a gallon nationwide. Mid-grade was pegged at $2.91, while premium-grade was at $3.01.

Decreased demand also played a role in the decline, Lundberg said Sunday. Sales were virtually nonexistent in flooded and storm-ravaged areas like New Orleans, while the price spike prompted drivers in other parts of the country to reduce consumption.

The survey was taken before Hurricane Rita (search) struck oil-producing Texas and Louisiana on Saturday, causing far less damage than had been feared. Before Rita hit, 16 refineries in Texas accounting for 2.3 million barrels per day of capacity shut down and evacuated crews.

"There will be some modest disruption of supplies of gasoline and other products," said William Veno, an analyst at Cambridge Energy Research Associates. "But I don't think it's going to be as severe a situation as Hurricane Katrina."

Pump prices for self-serve climbed to a record-high average of more than $3 a gallon after Katrina severed oil pipelines and damaged offshore platforms in the Gulf.

Four refineries in Louisiana and Mississippi whose output had been more than 800,000 barrels per day remain closed almost a month after Katrina, and a significant amount of oil and natural gas output has not returned.

However, other refineries are back online.

"Katrina damage remains a crimp on gas supplies, but we've had a major comeback by the oil industry since she hit," Lundberg said.

Among the stations included in the survey, the lowest price for unleaded regular was in Baton Rouge, La., at $2.57 a gallon. The highest was in Honolulu at $3.23.