The national average price of gasoline fell 2 cents to $2.55 per gallon, which is 5 cents lower than a month ago due to declining demand, according to AAA.

Gasoline demand has fallen to its lowest rate since the middle of February. At the same time, gasoline supply has reached its highest level since the summer, according to the U.S. Energy Information Administration. The Dec. 16 price level is 18 cents higher than the same time a year ago.

"As the weather turns colder, people tend to drive less and we see less gasoline demand," said Jeanette Casselano, AAA spokesperson. "This is causing gas prices to be less expensive. In the lead up to the holidays we may see a small spike in demand, but not enough to impact gas prices substantially."

States with the largest weekly changes include Michigan (down 9 cents), Idaho (down 9 cents), Indiana (down 8 cents), California (down 8 cents), Ohio (up 8 cents), Nevada (down 7 cents), Utah (down 7 cents), Florida (down 6 cents), Oregon (down 5 cents), and Washington (down 5 cents).

States with the least expensive markets now include Mississippi ($2.20), Missouri ($2.20), Oklahoma ($2.23), Louisiana ($2.23), Texas ($2.23), Arkansas ($2.25), Alabama ($2.25), South Carolina ($2.27), Kansas ($2.27), and Virginia ($2.29).

Meanwhile, the average price of a gallon of diesel fell 2.5 cents to $2.536, which is 16.7 cents higher than a year ago.