(CNN) - The average price regular gasoline rose half a cent during the past two weeks, to $1.88, a national survey said Sunday.

But the Aug. 27 survey results may portend a drop in the near future, said Trilby Lundberg, publisher of the Lundberg Survey, which tallies prices at about 7,000 gas stations.

Since Aug. 19, when the price of light sweet crude peaked at $48.70 a barrel, it has dropped $3.40, she said.

"That's because world supply caught up with strong world demand," she said. "What this means for gas is that, unless there is an actual shortage of crude oil on the near horizon, then currently lower crude oil prices will work their way into gas."

Lundberg predicted that gas prices would begin to drop in her next survey and continue to fall past Labor Day.

"There's downward pressure on gasoline already in the wholesale markets around the country," she said. "Already, some retail prices are down."

At the pump, average prices for self-serve regular have tumbled about 20 cents a gallon since hitting a peak of $2.07 on May 21, according to the latest survey. The average price is still about 16 cents a gallon higher than it was one year ago.

Drivers in Tulsa, Okla., paid the least, $1.72 a gallon for self-serve regular. Honolulu drivers paid the most, at $2.26.

Here are some other prices:

• Houston: $1.76
• Denver: $1.80
• Boston: $1.92
• Chicago: $1.99
• Long Island, N.Y.: $2.07
• San Francisco: $2.11