California gas prices keep U.S. average high October 7, 2012 -- Updated 1905 GMT (0305 HKT) The slight increase "masks a tremendous variation" nationwide, analyst says California refinery woes drove up West Coast prices, boosting the U.S. average The most expensive gas was in San Diego; the cheapest in Jackson, Mississippi (CNN) -- Average U.S. gas prices edged up a fraction of a penny over the past two weeks, buoyed by a sharp increase in California as other parts of the country saw declines, according to a survey released Sunday. The average price of a gallon of regular gasoline went up about 0.37 cents between September 21 and October 5, according to the Lundberg Survey of about 2,500 filling stations in the Lower 48 states. But that figure "masks a tremendous variation" across the country, survey publisher Trilby Lundberg said. "In most cities around the country, pump prices dropped as lower crude oil prices made their way all the way to the pump," Lundberg said. But at the same time, refining issues in California affecting gasoline supply caused huge price hikes there. A power outage at one California refinery and a fire at another cut into supplies for much of the state and some neighboring markets, driving pump prices up by nearly 39 cents per gallon during the past two weeks, Lundberg said. "Looking around the corner, we see wholesale prices declining, and this should spell the end of the price hikes at the pump in the near future," she said. Gas prices are up about 42 center per gallon since early October 2011, she said. The city with the cheapest average gasoline was Jackson, Mississippi, at $3.43 a gallon, according to the new survey. The most expensive could be found in San Diego, at $4.55. Here are average prices in some other cities: Atlanta: $3.62 Baltimore: $3.66 Baton Rouge, Louisiana: $3.50 Boston: $3.95 Chicago $4.04 Denver $3.69 Long Island, New York: $4.12 Minneapolis: $3.81 Portland, Oregon: $4.00 St. Louis: $3.46