California motorists on Friday were smacked by gasoline prices that shot up 15 to 20 cents a gallon overnight, and experts warned that the record-setting onslaught could continue through the weekend or longer.

The average price of regular unleaded gasoline statewide skyrocketed 17 cents between Thursday and Friday to $4.48 a gallon, according to AAA. That's 13 cents short of the all-time record set in June 2008, and is the highest average gas price in the United States.

The sudden spike is unprecedented in California history, said one petroleum analyst, brought on by a flurry of in-state refinery issues. Dwindling supplies forced some Southern California stations to close, and motorists had no choice but to foot the bill.

"Yeah, I'm mad. A lot of people are mad," said Sacramentan Pete Bowman, as he pumped his car full of regular for $4.65 a gallon at the 76 station at 15th and X streets. "This just feels like robbery, a price like this."

In Sacramento, prices ballooned 16 cents in 24 hours to a $4.36 average, AAA said. Unleaded regular in the Sacramento area just one week ago was $4.06 a gallon. A year ago, it was $3.78.

Patrick DeHaan, senior petroleum analyst at national gas price tracker GasBuddy. com, said Friday afternoon that the average price of all grades of gas in California hit a record $4.60 a gallon, edging the previous mark of $4.58 set on June 15, 2008.

DeHaan was among the analysts who forecast the statewide spike earlier in the week.

On Friday, he said the state had never seen anything like it, "in terms of how quickly this has happened, out of the blue, so to speak." However, he pointed out that it doesn't compare to the havoc that Hurricane Katrina wrought on gas prices nationally in 2005.

Analysts' estimates on how long the state's high prices will last were all over the map, but DeHaan offered up a sliver of hope for relief by early next week.

"Wholesale prices are heading the other way now (Friday). They're generally on a downhill coast," DeHaan said. He said it usually takes three to five days before changes in the wholesale price start to show up at the pump.

"I don't want to sound the all-clear bell yet, but once you get through the weekend, things might start looking a little better."

Gasoline horror stories were the order of the day throughout the state.

Numerous reports of stations posting $5-a-gallon gasoline rolled in – many in car-choked Southern California. In the south, at least a dozen Costco stations ran out of gas and closed their pumps.

Energy experts noted that Costco is an independent gas provider that gets fuel on the open market, unlike other major in-state gas providers that have their own refineries. Getting gas on the open market now is a pricey proposition, given low supplies.

Analysts said Costco also was affected by a rush of consumers looking to buy its typically cheaper gas, draining its underground tanks.

In the Sacramento area, gas stations continued to do business Friday, albeit serving some very upset customers.

"Do you believe this? I think it's the worst ever," said Bowman, at the 76 station. "I hear all the reasons why this is happening, but it never seems quite on the level."

Pumps showing $4.59 a gallon for regular at the nearby Valero station at Broadway and Riverside Boulevard were getting brisk business. But there were no smiling faces.

"What are you going to do? You have to live, keep moving, do your work … feed your family," said Sacramentan Eva Perez. "Of course I don't like it. I hate it. But I just can't stop living my life."

Oil companies tried to roll with the punches.

ExxonMobil and Valero Energy said they were rationing gasoline deliveries to customers in California in an effort to deal with supply shortages. Valero also stopped selling gasoline on the wholesale market in California.

Other companies talked of rationing, but they, like many energy analysts, are not sure when supplies and prices will swing the other way.

The price spike is specific to California, in part because the state has its own regulations for producing gasoline. California cannot import gas on short notice and is not connected to pipelines serving other states.

Nationally, AAA said the average price of regular unleaded on Friday was $3.78 a gallon, unchanged from last week and 4 cents lower than a month ago.

Today marks the one-month anniversary of the event that started California gas prices skyrocketing.

An Aug. 6 fire in a unit of a key Chevron refinery in Richmond, with a capacity of 245,000 barrels a day, prompted a 25-cent-plus rise in the average price of gas throughout California. That unit still awaits repairs, and Chevron has taken criticism from Bay Area residents and lawmakers alleging a lack of safety precautions.

From mid-August through last week, California gas prices stayed pretty much locked in place. Then on Tuesday, energy analysts started sounding the alarm.

A Monday power outage at ExxonMobil's 150,000-barrel-a-day refinery in Torrance disrupted its output. Also on Monday, Chevron's Kettleman-Los Medanos pipeline, which delivers crude to Bay Area refiners, was shut down after elevated levels of organic chloride were detected in the oil. The line is rated at 85,000 barrels a day.

In-state supplies were further limited by maintenance work at Phillips 66 facilities in the Bay Area and Southern California.

There was an encouraging bit of news Friday: ExxonMobil said its Torrance refinery has resumed normal operations and would be able to meet its commitments.

On another front, the Sacramento-based California Independent Oil Marketers Association has asked the state to expedite a waiver allowing refiners to produce and sell less expensive winter-blend fuel before the scheduled Oct. 31 switchover date.

That request to the California Air Resources Board is subject to a California Energy Commission review of fuel inventory. The state also is charged with estimating the air quality effects of such a move. State officials said that process is not an immediate fix, and there is no timeline for approval.

"We're evaluating the whole situation, basically," said ARB spokesman Dave Clegern. "(The CEC) has to determine inventory, how much gas is out there, is there any winter-blend gas to be had and how much, how much volume can be produced. … Can it happen in time to make a difference?"

Clegern said "it's quite the process," and the request is rare. He said the last time ARB had a similar request was in the aftermath of Hurricane Katrina.

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