(CNN) -- The U.S. average price for regular unleaded gasoline rose by nearly 12 cents in the past three weeks, marking the first increase in six months, according to a national survey released Sunday.

"It is the first rise since July 11 last year when prices hit their all-time high," said Trilby Lundberg, publisher of the survey.

The average price of self-serve regular unleaded gasoline is $1.78, according to the Lundberg Survey, which is based on responses from more than 5,000 service stations nationwide. The latest survey looked at prices January 9.

"The price had to hit bottom sometime," Lundberg said.

She said part of the reason for the price spike is recent indications of production cuts among OPEC members, which are aimed at driving up oil prices during a time of year when there is a decreased demand for gasoline.

"January historically is the lowest gasoline usage month," Lundberg said.

Despite the increase, gas prices are still $1.29 lower than they were on January 11, 2008, she said.

Drivers in Billings, Montana, had the cheapest gas on average, paying $1.34. Motorists in Anchorage, Alaska, paid the most, at $2.32.

All About OPEC • Billings (Montana)