Retail gas prices hit yet another record high over the past two weeks and could go even higher before the traditional post-Labor Day driving decline ends demands pressure, according to a nationwide survey.

While gas prices usually peak in August, any major disruption to oil production facilities in the Gulf of Mexico (search) caused by Hurricane Katrina (search) could keep prices high even longer. The storm was heading for New Orleans (search) Sunday with 175-mph winds and a threat of a 28-foot storm surge.

The average price for all three grades rose nearly 13 cents to $2.65 in the two weeks ending Aug. 26, said Trilby Lundberg, who publishes the semimonthly Lundberg Survey of 7,000 gas stations around the country. The figures were not adjusted for inflation.

That follows an increase of nearly 20 cents in the prior three weeks. Retail gas prices as measured by the survey have risen an average of 83 cents since early January.

The price increases were similar to the hikes seen in crude oil prices over the same period.

Although consumers have complained about the record gas prices, AAA (search) expects a 1 percent increase in the number of Americans taking road trips over the upcoming Labor Day holiday weekend.

That's not as high an increase as in previous years in large part because of higher prices and an increase in the number of school systems that resume classes before the holiday.

"This year, September demand might be a bigger falloff than usual because of the higher prices," Lundberg said Sunday.

The level of damage caused by Katrina may extend the price peak beyond Labor Day. Already, some production capacity has been idled because oil companies have evacuated personnel in the area.

"One certainly hopes this is not an Ivan-caliber hurricane that did in fact do long-term damage to U.S. production facilities in the Gulf and did contribute to tighter oil supplies," Lundberg said.

According to the survey, self-serve regular averaged $2.65 a gallon nationwide. Midgrade was pegged at $2.72, with premium-grade was at $2.82.

Among the stations included in the survey, the highest price for unleaded regular was in Chicago at $2.84. The best deal was in New Orleans at $2.45 a gallon.