Nvidia has led the S&P 500 ( ^GSPC -0.29%) higher this year amid frenetic interest in artificial intelligence (AI). The stock has surged 136% since January, and Wall Street analysts forecast median upside of 30% from the current share price of $115. But betting on a single AI stock is a bad strategy.

It’s Fed decision day—and it'll be difficult for the chip maker's shares to make gains until investors have more clarity about the central bank's next move.