The California Air Resources Board on Monday said the last time the state made an early shift to so-called "winter-blend" gasoline was in 2005, in response to supply disruptions caused by Hurricane Katrina.
AAA said the average price for a gallon of regular hit $4.668 Monday in California — the highest price in the nation.
Officials said it could take days before prices fall, depending on how quickly refineries can get the winter-blend fuel to market.
California usually converts to the gas on Oct. 31. The fuel evaporates in heat more quickly than summer-blends.
A fuel's evaporation rate indicates how much raw fuel enters the environment, especially in warm weather.