A late-August rally lost some sizzle Thursday, sapping major stock indexes of momentum as they enter a month that is traditionally their weakest of the year.

Investors still have confidence in the U.S. economy, as well as the potential for artificial intelligence to boost productivity gains, but stock markets fell for much of August before turning upward. The S&P 500 and Nasdaq Composite snapped five-month winning streaks, while the Dow Jones Industrial Average posted its first monthly loss since May.

Clayton Allison, a portfolio manager at Prime Capital Investment Advisors, said he has increasingly advised clients to eye small- and midcap stocks that could capitalize on a robust U.S. economy and limit any fallout should the outlook darken. “The consumer has been so resilient over the last three or six months,” he said. “A lot of people probably didn’t expect that with interest rates going up.”