After a slowdown in same-store sales this summer, Costco Wholesale bounced back stronger in September. There is, however, more to the story.

Comparable sales in the U.S., excluding impacts from gasoline prices and foreign exchange, rose 8% in September, up from 5% a year ago.

The numbers in September mark a solid rebound from a summer slowdown. Same-store sales rose 7.6% in August, 6.9% in July, and 6.3% in June. Not since May, when Costco posted a 8.7% increase in sales, has growth been at this level.

In July and August, comparable sales in the U.S. grew by 0.4% and 0.2%, respectively, from a year ago.

A calendar shift in 2026 provided an extra tailwind. Labor Day fell one week later this year, which boosted sales in September by 50 basis points, Costco said. Management had previously said that a later Labor Day contributed to a slight weakness in sales in August.

Higher foot traffic also contributed to strong sales in September. Stores in the U.S. saw shopper visits increase by nearly 4% in September, up from about 3% in August.

While growth picked up in September, that figure has a bit of nuance. Mizuho analyst David Bellinger wrote Thursday that some of the lift came from one-off factors -- DoorDash and Uber Eats gift card sales -- and lower-margin categories such as the food court and pharmacy, which aren't as profitable as core retail merchandise. The firm has an Outperform rating and $1,065 price target on Costco stock.

Costco stock rose 1.1% to $952.63 in premarket trading Thursday. Shares have risen nearly 10% this year, but the stock has pulled back almost 14% from its 52-week closing high of $1,094.32 on May 19, according to Dow Jones Market Data.

The strong performance in September signals that Costco's operations remain healthy, with performance meeting expectations. Investors will likely continue to watch and see whether that momentum can also translate to continuous membership growth.