The nearly 40 million Americans expected to hit the roads this Memorial Day weekend will have something to make them smile while sitting in traffic: cheap gas prices.

Fuel price app GasBuddy says the cost for a gallon of unleaded jumped 17.3 cents in the last week, and there are a couple of reasons why.

The EIA reports that the national average for a gallon of regular gas is $3.12, down 13.5% over the past year.