UBS' Art Cashin expects that markets could retest 3900 in a couple of days, possibly even challenge the bear market bottom, and warned investors to beware the autumnal equinox. "I think we may even go back and retest the June lows," Cashin said Tuesday on CNBC's "Squawk on the Street." "Certainly the 3900 is just so tempting and pulling back below the 50-day moving average here, it's very much about the technicals. ... It meant a lot of guys who are making preliminary favorable bets got caught off base and they had to purge it out in the opening. And I think my yardstick tells me we will probably have a minor downswing now that will last several days and see where we go," he added. The director of floor operations for UBS Financial Services made his comments as markets plunged Tuesday after a hotter-than-expected inflation report had traders fearing greater interest rate hikes for longer from the Federal Reserve. The central bank is meeting next week just as cooling energy prices had many investors believing inflation had peaked. Cashin advises investors keep an eye on the next moves from the Federal Reserve, as well as what's going on with central banks abroad. He also warned traders to prepare for more choppiness ahead, as the September-October months are a seasonally brutal period for markets. "The next swing over the bottom can be somewhere around the autumnal equinox... So there's a chance that this leg down can last actually that long? I doubt it, but it can," he said. The autumnal equinox occurs on September 22nd this year and is when the sun crosses directly above the equator while moving south. "We want to see what happens around the time of the autumnal equinox when they would be due to try for one last move to the upside before going into rather ugly October," he added.