Art Cashin is warning investors to keep a close eye on key thresholds in the S & P 500 as markets approach a "critical time." "We're testing and retesting both bond yields and the level in the S & P … if there is a sudden change, if there's a breakout, then it could take the market by surprise and you could have a big move," the director of floor operations at UBS Financial Services told CNBC's " Squawk on the Street " on Friday. Cashin pointed to the 4,440 to 4,535 range as a key level to watch as the index tests some major moving averages, with the index currently sitting in that area at around 4,456. August, he added, historically ushers in "changes in direction." The comments from Cashin come as the market rally in 2023 has shown some signs of cooling over the past two weeks as investors grapple with fresh inflation data and a recent U.S. credit rating downgrade from Fitch. While up 16% year to date, the broad-based index sits 3% lower for the month and is on track to cap off the week with a loss. "I've been doing this a long time and I will tell you whenever it looks like the book is over, there's one more chapter," Cashin said, adding that it may be too early for the bulls to "emerge victorious."
