NEW YORK – A surprise surge in gasoline prices is taking some of the fun out of summer. And Indiana leads the pack of party poopers.

The national average for a gallon of gas at the pump has climbed to $3.67, a rise of 34 cents since July 1. But prices in the Hoosier state shot up by 59 cents during the six-week period.

Ohio, Michigan and Illinois have all seen prices spike well above the average, analysts say.

An increase in crude oil prices and problems with refineries and pipelines in the West Coast and Midwest, including a fire in California, are mostly to blame.

Analysts don’t expect gas prices to get as high as they did in April, when 10 states passed $4 a gallon and the U.S. average topped out at $3.94. But this is still unwelcome news in this sluggish economy, because any extra money that goes to fill gas tanks doesn’t get spent on movies and dinners out.

The price at the pump in the U.S. fell more than 60 cents a gallon during the spring as the global economy slowed and turmoil in the Middle East seemed to subside.

But crude oil is climbing again, rising to $94 a barrel from a low of $78 in late June. Production outages in South Sudan and the North Sea, Western sanctions that have cut the flow of Iranian oil, Iran’s threat to block tankers passing through the vital Strait of Hormuz, and fears that the violence in Syria could escalate into a wider regional conflict have driven up oil prices.

Seasonal factors are also sending pump prices higher.

Gasoline usually costs more in the late spring and summer because refiners have to make more expensive blends of gasoline to meet clean air rules and because the summer driving season boosts demand.