The US national average gas price hit $4.018 a gallon on Tuesday, crossing the $4 threshold for the first time since August 2022, according to the American Automobile Association. That’s roughly a 35% jump, or $1.04 more per gallon, since the Iran war began in late February. Diesel has surged even more sharply, rising about 45% to $5.45, raising concerns about higher shipping, grocery, and consumer goods prices.

With the Strait of Hormuz — through which roughly a fifth of global oil supply previously flowed — effectively closed, crude prices are up more than 50% since the war began, feeding quickly into pump prices across the US.

Still, regional differences remain, with drivers in California now facing nearly $5.90 a gallon for regular gasoline, followed by Hawaii ($5.50) and Washington ($5.30), while those in Oklahoma, Iowa, and Kansas pay under $3.30 a gallon.

Prices could even approach $5 nationwide if the strait remains blocked, Patrick De Haan, head of petroleum analysis at GasBuddy, told CNBC.