ATLANTA (CNN) - The average price of a gallon of self-serve regular gasoline rose less than four cents over the past two weeks, to $2.95, but still dropped slightly or significantly in 26 cities, according to a survey out Sunday.

"Gasoline prices are down in nearly all of the wholesale markets and even in many retail markets as well," said Trilby Lundberg, whose Lundberg Survey tallied prices at about 7,000 gas stations Friday.

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The average increase of 3.69 cents was a small fraction of the increase of more than 25 cents reported in the April 21 survey, when the price was boosted by the rising price of crude oil and tight supplies.

In the past two weeks, crude oil prices have dropped about $5 a barrel, Lundberg noted.

Coupled with an increase in total gasoline supply in that time, she said, "what was an extreme convergence of 'up' price influences in recent weeks is now a prescription for peaking prices, at least in the short term."

But, she warned, "it might only be temporary, because we are still heading into our highest gasoline demand period of June, July and August," and gas producers remain under strain from factors such as government mandates on blending a certain amount of ethanol into gasoline.

San Diego drivers are paying the highest price at $3.41 a gallon -- up 29 cents from two weeks ago, when the city also was the most expensive. Cheyenne, Wyo., posted the lowest prices, averaging $2.61. Two weeks ago the lowest average price was $2.54, found in Boise, Idaho.

Other averages included $2.91 in Houston; $2.97 in Portland, Ore.; and $2.93 in Boston.

Since the Jan. 6 survey, the nationwide average price of a gallon of self-serve regular has gone up 65 cents, Lundberg said. Two-thirds of that increase occurred in April.

She said the following cities are among those posting price decreases over the past two weeks:

-- Atlanta, $2.85, down about five cents;

-- Cleveland, $2.82, down about four cents;

-- Des Moines, Iowa, $2.76, down about 10 cents;

-- Detroit, $2.80, down about seven cents;

-- El Paso, Texas, $2.79, down about five cents;

-- Indianapolis, $2.83, down about seven cents;

-- Jackson, Miss., $2.77, down about 10 cents;

-- Milwaukee, $2.98, down about seven cents;

-- Pittsburgh, $2.94, down about two cents;

-- St. Louis, $2.69, down about 10 cents.

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