U.S. stocks traded lower Friday, a day after the S&P 500 index closed at a record high. Before the start of the long Memorial Day weekend, investors and market professionals are looking to a speech Friday afternoon from U.S. Federal Reserve Chair Janet Yellen for any clues as to the timing of the central bank's next interest rate hike.

Yellen is scheduled to talk about the state of the U.S. economy at the Greater Providence Chamber of Commerce in Providence, Rhode Island, at 1 p.m. EDT.

The Dow (INDEXDJX:.DJI) dropped 57.25 points, or 0.31 percent, to 18,228. The Standard & Poor's 500 (INDEXNASDAQ:.IXIC) dipped 4.07 points, or 0.19 percent, to 2,127. The Nasdaq composite (INDEXSP:.INX) lost 3.01 points, or 0.07 percent, to 5,087.

Yellen's talk is especially timely in light of Friday's report showing that U.S. consumer prices edged higher in April. The rise in core inflation could give the Federal Reserve ammunition to raise interest rates this year if it continues to pick up. The latest minutes from the Fed’s April meeting, released earlier this week, revealed the central bank ruled out June as a timetable for a hike in interest rates. Most economists anticipate the central bank will hike rates in September.

The Consumer Price Index rose 0.1 percent last month from 0.2 percent in March, the Labor Department said Friday. Core CPI, which excludes volatile components such as food and energy, gained 0.3 percent in April, the biggest monthly gain since January 2013, after rising 0.2 percent in March.

“The Fed can't wait forever before beginning to raise interest rates from near-zero. September is still the most likely lift-off date, but July is not out of the question, particularly not if we get another couple of robust rises in core consumer prices in May and June,” Paul Ashworth, chief economist at Capital Economics, said in a research note Friday.

Friday's declines were led mostly by transports, as the Dow Jones Transportation Average fell around 1 percent, led by a 1.5 percent drop from United Continental Holdings Inc. (NYSE:UAL). 

Boeing Co. (NYSE:BA) led the Dow lower Friday, losing more than 1 percent, while iPhone maker Apple Inc. (NASDAQ:AAPL) was the largest gainer in the blue-chip index, up nearly 1 percent.

The S&P 500 utility sector was the biggest decliner, shedding 0.5 percent as natural gas and electricity company PG&E Corporation (NYSE:PCG) lost 1 percent.

Campbell Soup Company (NYSE:CPB) rose 2 percent after the seller of Pepperidge Farm snacks beat Wall Street profit forecasts, boosted by lower promotions. The company unveiled an aggressive cost-cutting plan in February that would save Campbell Soup’s at least $200 million annually over the next three years.

Shares of Aeropostale Inc. (NYSE:ARO) tumbled 12 percent Friday to a 52-week low of $2.13, after the struggling teen apparel retailer posted a 20 percent drop in sales that resulted in a quarterly loss. The company has been facing multiple issues and was hurt by its merchandise assortment, unseasonably cool weather and the West Coast port slowdown. 

Jessica Menton is a writer who covers business and the financial markets. News tips? Email me here. Follow me on Twitter @JessicaMenton.