The national average price of a gallon of regular unleaded jumped 12 cents to $2.93 over the past two weeks, ahead of the Memorial Day holiday and reaching the highest level for this holiday weekend in four years, according to AAA.

The price level, which also increased six cents in the past week, is the highest since Memorial Day weekend in 2014, when gasoline averaged $3.65 per gallon. Nearly 37 million travelers are expected to hit the road this year for the holiday.

"Compared to an average of the last three Memorial Day weekends, pump prices are nearly 50 cents more expensive and climbing," said Jeanette Casselano, a AAA spokesperson. "Trends are indicating that this summer is likely to bring the national average to at least $3 per gallon."

As of May 21, gasoline averages more than $3 per gallon in 14 states, including Idaho, Utah, Connecticut, Pennsylvania, New York, Illinois, and Michigan. Several West Coast states are also above that level.

Among the states, the largest monthly increases have come in Minnesota (28 cents), Wisconsin (27 cents), Missouri (25 cents), Connecticut (23 cents), Delaware (23 cents), and Illinois (23 cents).

California tops the list of the nation's most expensive markets with an average price of $3.71 per gallon. Others include Hawaii ($3.68), Washington ($3.41), Alaska ($3.36), Nevada ($3.32), and Oregon ($3.31).

Meanwhile, the average price for a gallon of diesel increased 3.8 cents to $3.277, which is 73.8 cents higher than a year ago, according to the U.S. Energy Information Administration.

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