Slow Downward Trend, But Eureka and Yreka Still Report $2 Per Gallon As the summer driving season winds down, AAA today reported gas prices in Northern California are starting to cool down from their record high set last month. The average price for a gallon of regular unleaded self-serve gas in Northern California, according to AAA's monthly gas survey, is $1.85, down 3 cents from the record-breaking $1.88 set last month, but 20 cents higher than a year ago.