The cost of gasoline in Massachusetts is bucking historical trends and dropping as the summer driving season gets underway.

AAA Northeast said Monday that self-serve, regular gasoline is selling for an average of $2.67 per gallon, 4 cents lower than a week ago.

The current price is a penny lower than the national average and 20 cents lower than last year’s average in Massachusetts.

A spokesman for AAA says a decline in prices at this time of year is unusual, because higher demand in the summer usually drives prices higher. This year, growing gasoline inventories are contributing to lower prices.

AAA found a wide range in prices, from a low of $2.49 per gallon, to a high of $3.05 per gallon.