"I think the market will react to outliers, if it's particularly weak versus expectations. The idea that manufacturing in China is slowing I think is baked into the market," Lafferty said.
Wednesday also marks the effective date for the full inclusion of U.S.-listed Chinese firms in MSCI's global indexes. Separately, speculation around MSCI's scheduled June 14 decision on including mainland-listed A shares sent the Shanghai composite up more than 3 percent Tuesday.
Other data scheduled for release Wednesday include May auto sales, April construction spending and the Fed's Beige Book. Michael Kors, Cracker Barrel, Lands' End and Vera Bradley are among the few names due to report earnings before the bell, while Analogic, Box and Semtech are scheduled for after the close.
Read MoreExpert: June gloom ahead as volatility remains low
"In anticipation of the Fed meeting coming up, I find it very difficult to believe any money managers are going to make any significant moves in between earnings [seasons]," said Jeff Reeves, executive editor of InvestorPlace.com.
June is historically one of the least volatile months of the year, according to analysis from S&P Global Market Intelligence U.S. Equity Strategist Sam Stovall. In a note Tuesday, he said since 1945, June is second only to December in showing the lowest monthly range of price fluctuations.
Presidential election years also tend toward less volatility in June, Stovall said in the note. Since 1952, when the incumbent was not running, the month saw the fewest number of days with a more than 1 percent decline in the S&P 500.