Motorists are getting a break on gasoline costs as the summer driving season begins, two pump price reports said Tuesday.

The average price for a gallon of regular gas in Santa Rosa dipped to $3.97, down nine cents from last month, according to AAA Northern California's monthly survey.

A year ago, local drivers were paying $4.13 a gallon, the AAA said.

All 25 areas in the survey saw prices fall at least two cents to 16 cents in the past month, and the statewide average price drop was six cents — with a $3.96 statewide price on Tuesday.

"Statewide lower prices are expected to continue through June, barring any unforeseen event," said Cynthia Harris, AAA Northern California spokeswoman.

Increased refinery production, steady crude oil prices and lower consumer demand are driving the trend, she said.

Regular gas was as low as $3.83 a gallon in Santa Rosa on Tuesday, the website said.

Meanwhile, the U.S. Energy Information Administration said regular gas would average $3.53 a gallon nationwide over the summer driving season from April through September.

The annual average price in 2013 is expected to be $3.49, down from $3.63 last year, the agency's Short-Term Energy Outlook said.

It forecast a nationwide average price of $3.37 a gallon in 2014, attributing the decline to lower crude oil prices.

California runs on some of the steepest gasoline prices in the nation, typically 20 to 40 cents a gallon higher than the national average.

The projected drop in Brent crude oil from $112 per barrel in 2012 to $105 this year and to $100 in 2014 "accounts for most of the gasoline price drop," said Tancred Lidderdale of the Energy Information Administration.

Increased crude oil production in the United States, Canada, Colombia and Brazil is expected to exceed the growth in world consumption and is "a significant contributor to the projected decline in crude oil prices," Lidderdale said.

U.S. oil production is expected to reach 7.3 million barrels per day this year, up from 6.5 million in 2012, and to hit 8.1 million in 2014.