(Portland, OR) -- Gas prices continue to rise. In Oregon, the average increased nine cents to $3.86 a gallon, while the national average increased a dime to $3.37. The AAA reports the increases are driven by refinery maintenance and the switch to more expensive and less polluting summer blends of fuel.

In Oregon, prices also increased because locks at dams on the Columbia River are closed, which prevent fuel barges from moving through. Maintenance on the locks is supposed to end later this month.