MADISON, Wis. – A rare combination of pipeline and refinery problems has exacerbated already rising gas prices in the Great Lakes region, leading to surges of around 35 cents per gallon in just one week, officials said Friday.

Michigan’s statewide average price for a gallon of regular unleaded rose 34 cents during the past week to $3.95, making for the highest per-gallon price in the continental U.S, according to auto club AAA. The week’s average per-gallon increase in surrounding states ranged from 26 cents in Wisconsin to 33 cents in Illinois and Indiana.

The national average price for a gallon of unleaded, by comparison, moved up just 8 cents over the week to $3.56.