Contra Costa County's average gas price hit $6.32 per gallon on Friday, Sept. 25, up 78 cents in six weeks and climbing fast enough to squeeze household budgets across Walnut Creek.
The county average rose 21 cents in a single week, from $6.11 on Sept. 17 to $6.32, according to Contra Costa News citing AAA data. On Aug. 14, the county average sat at $5.54.
California's statewide average reached $6.23 on Sept. 25, up 61 cents from a month ago and $1.58 higher than the same time last year. The state remains the most expensive gasoline market in the country, according to AAA.
Among Bay Area cities AAA tracks, only San Francisco, at $6.40, was higher than Contra Costa County. Oakland averaged $6.28, San Jose $6.23 and Sacramento $6.17.
The county price is closing in on California's all-time record of about $6.44 per gallon, set in June 2022, the Sacramento Bee reported.
Why prices keep climbing
Doug Johnson, spokesperson for AAA Mountain West Group, said autumn typically brings lower gas prices. That pattern has not held in 2026.
"Typically, the start of autumn brings lower gas prices, but lingering volatility in the Strait of Hormuz and the high cost of crude oil are driving up pump prices," Johnson said in the Sept. 25 report.
The Strait of Hormuz, a narrow waterway between Iran and Oman, carried about 20% of the world's oil supply before the U.S.-Israel conflict with Iran disrupted shipping there, according to Marine Link. West Texas Intermediate crude settled at $92.16 per barrel on Sept. 23, up $1.64 on the day.
A diplomatic opening emerged on Sept. 25. Iran's Foreign Minister Abbas Araghchi proposed reopening the strait within seven days and restarting nuclear talks, Bay Street reported. Crude prices fell about 2% on the news.
Whether that translates to lower prices at local gas stations remains uncertain. The national average hit $4.48 per gallon as of Sept. 24, the highest ever recorded for this time of year, according to AAA. The September monthly average of $4.30 already tops the previous September record of $3.83, set in 2023.
Diesel drivers face an even steeper bill. California's diesel average reached $8.44 per gallon on Sept. 25, up from $7.18 a month earlier.
