Gas prices have once again risen over the last week in the Treasure State.GasBuddy.com reports average gasoline prices in Montana have jumped 7.7 per gallon in the last week and are averaging $2.86 per gallon as of Monday, Jan. 20, 2025.Gas prices are now 10.8 higher in Montana than a month ago and 0.9 per gallon higher than a year ago. The national average price of gasoline has fallen 6.5 per gallon over the last week to $3.09 per gallon, which is 4.5 higher than a month ago.GassBuddy.com reports the cheapest gas in Montana was at $2.73 per gallon on Sunday while the most expensive was $3.09 per gallon.