Wall Street finished flat on the last trading day of a volatile month. Strong consumer spending data in July initially drove the markets higher, but investors later chose to take profit friday ahead of a long Labor Day weekend. The S&P inched up 1 tenth of a percent on the day; for the month, it lost 1.8%.

Helios Quantitative chief investment officer, Joe Mallen:

SOUNDBITE: HELIOS QUANTITATIVE CHIEF INVESTMENT OFFICER, JOE MALLEN (ENGLISH) SAYING:

"There are these looming unknowns over the weekend whether we're going to add additional tariffs to China, we've got a massive storm coming in, people are just a little bit jittery but no one really wants to make a trade in either direction."

Ulta Beauty had an ugly day. The high-flying shares lost more than a quarter of their value after the cosmetics and skin care retailer warned sales would slow and cut its profit forecast for the full year.

The biggest gainer on the S&P 500 was Campbell Soup. The food maker sold more soups and snacks and cut costs during the quarter. Its earnings and margins beat Wall Street's forecasts.

Shares of Tesla rose for a third straight day. China said it will exempt 16 Tesla electric vehicles from its 10% purchase tax.