CHICAGO (CBS) — Chicago area gas prices jumped 25 cents at some stations in one day this week, thanks to a double-whammy of refinery problems and the switchover to summer blend gasoline.

WBBM Newsradio’s John Cody reports, with a gallon of regular unleaded now going for an average of $4.70 per gallon, Chicago’s gas prices are even higher than Hawaii’s.

Gas Buddy analyst Patrick DeHaan said BP and ExxonMobil have said maintenance being completed at Whiting and Joliet has restricted local gas supplies, just as refineries switch to the more expensive summer blends, and driving demand picks up for the holiday season.

“Unfortunately, it may get worse before it gets better, but in the next two weeks or so, we should see some relief, starting that is, in the next two weeks,” he said.

DeHaan said several stations raised their prices by a full quarter per gallon between opening and closing on Wednesday.

Daniel Vargas fills his vintage Camaro with premium. That grade carries a premium price, even in northwest Indiana, where gas is normally cheaper.

A gallon of premium was going for $4.89 at one Merrillville, Ind. gas staion.

“Northwest Indiana is not the place to get cheap gas. In fact, there’s no cheap gas and there hasn’t been for quite some time,” DeHaan says. “Tighter gasoline supply combined with these refinery outages creates a very tight situation for supply. And what happens? Econ 101 says prices go way up.”