The national average cost for a gallon of regular unleaded on Monday was the highest since August of last year.

“Prices may move a little higher in the coming weeks,” said Mark Jenkins, spokesman for AAA. “However the end is likely in sight for many drivers across the country. The exception to this trend could be motorists in regions where unexpected refinery or distribution issues cause prices to temporarily spike.”

The Ocala (Fla.) Star Banner reports that every spring refiners are required to switch to producing summer-blend gasoline by May 1, with gasoline required to be sold at the pumps by June 1. This seasonal refinery maintenance and the actual changeover itself increases the possibility of a disruption to production, which can send prices higher in an area that is normally supplied by a limited or offline facility.

Monday’s national average for a gallon of regular unleaded gasoline is $3.58, 3 cents more than last week.