YAKIMA, Wash. — Gas prices continued their expensive climb in the last week, rising 9.1 cents a gallon for regular unleaded to an average of $3.47 in Yakima, online fuel tracker GasBuddy.com reported Monday.

The national average increased to $3.68 a gallon, or 11.9 cents more than a week ago.

In the Yakima area, the online company surveyed 91 stations.

Prices Sunday in Yakima were 21 cents per gallon higher than a month ago but 4.2 cents below a year ago.

“The steady climb of retail gas prices is likely to continue following double-digit increases in wholesale prices with fuel production tightening in the majority of the country’s refineries,” GasBuddy.com Senior Petroleum Analyst Gregg Laskoski said in a news release.

Other average prices reported around the country were $4.28 in Los Angeles, $4.09 in Chicago and $3.86 in Detroit.