Memorial Day traditonally ushers in the summer season, and this year Americans will be traveling in droves. Some 37.2 million of them will head out of town that holiday weekend, AAA predicted Friday. That's the highest number since 2005 and a 4.7 percent increase over last year. AAA defines the Memorial Day weekend as the period between Thursday, May 21, to Monday, May 25.

Most of the weekend getaways will be by road: 33 million Americans are expected to drive. That's 5.3 percent more than last year. (Air travel is up too: 2.6 million Americans will fly, up 2.5 percent from last Memorial Day weekend.) 

"Following a harsh winter, many Americans are trading in their snow boots for flip-flops and making plans to start the season with a vacation getaway," AAA President Marshall L. Doney said in a statement. "AAA is expecting more Memorial Day travelers this year than any time in the past 10 years as confident consumers come out of hibernation ready to explore national parks, beach destinations and America's great cities."

One reason for the surge? Gasoline prices are likely to be the lowest they've been for most drivers in at least five years. The national average price per gallon of gas is currently $2.66 -- a full dollar below the average price on Memorial Day last year. 

"A strong employment market and low gas prices have driven consumer optimism to new highs and boosted Americans' disposable income. This is welcome news for the travel industry," Doney said.

The cost of airfare is a bit lower too: According to AAA's Leisure Travel Index, the average airfare for the top 40 domestic flight routes is $222, about 2 percent cheaper than last year. 

But travelers may not be as happy when they get to their destinations, with the cost of lodging seeing a slight uptick. Two-star hotels will average $144 a night, a 16 percent increase over last year, while three-star hotels will average $182, a 7 percent increase on the same basis.