The average price of a gallon of regular-grade gasoline jumped 8 cents nationally over the past three weeks, to $2.40.
Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that the spike results from higher crude oil prices.
The current price is 23 cents above where it was a year ago, but well below where it was in mid-August of 2015, 2014, and 2013.
Gas in San Francisco was the most expensive in the contiguous United States at an average of $3.02 a gallon. The cheapest was in Jackson, Mississippi, at $2.08 a gallon.
The U.S. average diesel price is $2.57, up 6 cents over the past three weeks.