The summer driving season will end much like it began, with American motorists paying the highest price at the gasoline pump in four years.

Gas prices have barely budged this summer, with the national average for regular gasoline hovering around $2.85 a gallon since mid-June. That's down slightly from a high of nearly $3 at the end of May, but it's still about 43 cents a gallon more than drivers paid at this time last year.

Analysts warn that Americans shouldn't expect much relief beyond Labor Day.

"I'm expecting towards the latter half of September gasoline prices will come off 10 cents a gallon," said Andrew Lipow, president of Lipow Oil Associates. "I think that they will be a little bit more elevated than in previous years."

Analysts say that's largely due to looming U.S. sanctions on Iran, the world's fifth-biggest oil producer.

Read more in CNBC.