Edmunds, the leading car shopping and information platform, forecasts that 1,527,363 new cars and trucks will be sold in the U.S. in May for an estimated seasonally adjusted annual rate of 16.8 million. This reflects a 7.5 percent increase in sales from April 2017 and a 0.3 percent increase from May 2016.

"Generous incentives are keeping traffic flowing to dealer lots, but a lot is riding on Memorial Day sales for automakers to keep momentum strong through the critical summer selling months," said Edmunds Executive Director of Industry Analysis Jessica Caldwell. "As long as high inventories continue to drive attractive deals and the economy remains strong, consumers will be in a great position to take advantage of a buyer's market this summer."

Edmunds estimates that retail SAAR will come in at 13.5 million vehicles in May 2017, with fleet transactions accounting for 19.6 percent of total sales. An estimated 3.3 million used vehicles will be sold in May 2017, for a SAAR of 38.3 million (compared to 3.4 million — or a SAAR of 38.3 million — in April).