Iowa's average gas prices have risen $.02 a gallon from a week ago. Triple A says Iowa drivers are paying $2.31 for regular gas. The cost per gallon across the country is $2.35, up a penny. The Davenport area continues to post the cheapest prices statewide at $2.20 a gallon for regular, followed by Sioux City at $2.23. It costs Des Moines drivers a state-high $2.40.