Chrysler, Nissan and Toyota all reported double-digit sales gains over last May. Even General Motors, battling bad publicity from a mishandled recall, surprised with a 13 percent sales increase.
Ford's sales rose a better-than-expected 3 percent. Of major automakers, only Volkswagen's sales fell. Volkswagen sales were down 15 percent as the brand prepared to launch the new Golf compact car.
May is traditionally a strong month for the auto industry. This year's calendar, with five weekends, gave it an extra boost. Sales were particularly strong the last weekend of the month, automakers said.
Analysts were expecting sales to rise 7 percent to 8 percent to 1.56 million in May, helping erase doubts about the strength of the industry. January and February sales were weaker than expected as consumers spent more time shoveling snow than shopping.
"We're still recovering from the low first-quarter numbers that we saw," said Jeff Schuster, executive vice president of forecasting for LMC Automotive, an industry consulting firm. "It's the continued recovery in the summer selling season, kind of everything aligning in the month of May."
Schuster said last month's sales were strong even without big discounts by automakers. Car buying site TrueCar.com estimated incentives were flat from last May and up 4 percent from April to $2,677 per vehicle. TrueCar said Hyundai, Kia and Honda had the biggest increases in incentives in May. Chrysler, GM and Nissan offered fewer deals.
GM said May was its best month since August 2008. Sales of its GMC Yukon and Buick Encore SUVs more than doubled, and buyers snapped up the new Chevrolet Corvette. GMC Sierra pickup sales gained 14 percent, while Chevrolet Silverado sales rose 8 percent.
Toyota's sales increased 17 percent over last May. Nissan's sales jumped 19 percent on strong demand for new vehicles, including the Sentra small car and Rogue SUV.
Chrysler's sales rose 17 percent, boosted by strong demand for the new Jeep Cherokee small SUV. Chrysler said its Jeep brand sales jumped 58 percent and set an all-time monthly sales record, with 70,203 vehicles sold in May.
Ford said it was a record month for the Fusion sedan and Escape SUV, which both topped 30,000 in sales. Sales for the Lincoln luxury brand gained 21 percent as the new MKC small SUV went on sale.
But Ford's truck sales dropped 4 percent as the automaker cut back on incentives. Ford said it's trying to manage pickup truck inventories in preparation for plant shutdowns as it changes over to its new aluminum-clad F-150 pickup, which is due out later this year. Ford plans to close its truck plants for a total of 13 weeks this year. It would normally make around 90,000 trucks in that time.
"If we really wanted to, we could sell more trucks in the near term, but we've got to manage this thing through," said Joe Hinrichs, Ford's Americas chief.
Auto sales have led the uneven U.S. economic recovery for the last few years, and Schuster expects that to continue. But the pace is expected to slow as annual sales top a natural peak of around 16 million. U.S. auto sales totaled 15.6 million in 2013, up from 10.4 million at the depths of the recession in 2009.