LOS ANGELES — Californians woke up to a shock Friday as overnight gasoline prices jumped by as much as 20 cents a gallon in some areas, ending a week of soaring costs that saw some stations close and others charge record prices.

The average price of regular gas across the state was nearly $4.49 a gallon, the highest in the nation, according to AAA’s Daily Fuel Gauge report.

In Southern California, the price jumped 20 cents a gallon overnight to $4.53 in Ventura. And in the Los Angeles-Long Beach area, prices went up 19 cents to nearly $4.54. It wasn’t any better to the north, as a gallon of regular gas in San Francisco averaged nearly $4.60.

In many areas, prices have jumped 40 cents in a week as refinery problems have created shortages and helped send wholesale prices soaring.

Among the recent disruptions, an Aug. 6 fire at a Chevron Corp. refinery in Richmond left one of the region’s largest refineries producing at a reduced capacity, and a Chevron pipeline that moves crude to northern California also was shut down. There also was a power failure that affected an Exxon Mobil Corp. refinery in Torrance, but the refinery has resumed normal operations

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