PALM SPRINGS, Calif. -

The average price of a gallon of self-serve regular gasoline in the Inland Empire -- which includes the Palm Springs desert resort areas -- decreased 2.4 cents today to $4.137, dropping for the 18th consecutive day and 21st time in 22 days.

Track the 10 least-expensive places to buy gas in the Coachella Valley with the KESQ.com Gas Tracker.

The average price in Riverside and San Bernardino counties has dropped 23.3 cents over the past 22 days, including 1.7 cents on Thursday, and is 10.8 cents less than one week ago and 6.4 cents lower than one month ago, according to figures from the AAA and Oil Price Information Service.

However, the average price is 18.4 cents more than one year ago.

"Drivers should absolutely be aggressively shopping around for the best gas prices  close to their normal commutes right now, because even though all local average prices are well above $4 a gallon, almost every area in Southern California has gas stations with prices of $3.99 or less," said Jeffrey Spring of the Automobile Club of Southern California.

"California prices are now below those in Oregon and Washington, which have had some continued refinery production issues."

California prices are customarily the highest in the 48 contiguous states.