Gasoline prices have risen up to 15-cents a gallon in the past month at many Iowa service stations. Dawn Duffy, spokeswoman for Triple-A Motor Club of Iowa, says two factors are to blame. Duffy says the colder weather is forcing refineries to make more home heating oil and less gasoline. Also, crude oil prices are way up. She says the significant price hikes seen in Iowa during the past month were -not- entirely expected. She says it did catch them by surprise, but it’s typical that prices go up when there’s a cold snap. Duffy says it’s hard to look into the crystal ball and predict where gas prices will go from here. She says they’ll watch weather and the price of crude oil. She says the OPEC nations will meet in February after saying they won’t cut back supply. The statewide average for a gallon of self-serve unleaded is a dollar-54. A month ago, it was a dollar-41. The national average is a dollar-58, up from a dollar-47 a month ago.