Stay up to date with our Up First newsletter, sent every weekday morning.

Drivers are starting to see some relief from high fuel prices. For the first time in months, the average price of a gallon of gasoline has dipped below $4, according to AAA.

The price crossed below the $4 threshold on Tuesday, and is currently down to a national average of $3.94 for a gallon of regular. Prices have dipped about 40 cents over the past month, with much of that decline happening in the past two weeks.

“Many will assume the election had something to do with it, but that’s a myth,” Patrick De Haan, head of petroleum analysis at GasBuddy, wrote in his industry newsletter.

Instead, he continued, gasoline prices are dropping for a more banal reason: “For now, it’s the seasonal shift, not politics, driving the relief at the pump.”

Gas prices often ease in the fall.

One reason: It’s no longer summer, which is the peak season for gas. (Fewer people drive in colder weather, AAA points out.) With less demand, there’s a touch more gas on the market.

Refineries also finish their annual maintenance by late fall. So that adds a bit more gas to go around.

And the blend of gasoline that’s on the market gets cheaper.

Refineries make two types of gasoline every year: summer and winter blends. The summer blend produces less smog, because it evaporates less quickly in the heat; the winter blend helps engines start up in freezing weather, and uses a bit more butane, which helps lower its cost.

(Normally, the switch happens around September 15. This year, the Environmental Protection Agency and the Department of Energy said the switch would happen on September 1, citing gasoline prices that have been driven up by the war in Iran.)

But none of those are the biggest reason why gas prices are falling, says Jorge León, head of geopolitics at the research group Rystad Energy. The main driver is the falling price of Brent crude oil, which is now down to about $90 a barrel, and which is what refineries need to make gasoline, diesel and jet fuel.

That price is falling because there’s a bit more oil coming out of the Middle East via pipelines, and because market traders have rejoiced at the intensifying diplomatic efforts between the U.S. and Iran.