Wall Street had a blockbuster second quarter. Big banks are cautioning that the sequel won't compare.

In the second quarter of the year, the biggest U.S. banks saw surging profits thanks to a boom in stock-market debuts, mergers and acquisitions and trading activity. Banks reaped the rewards of SpaceX's historic initial public offering, while market volatility kept trading floors bustling.

Executives are now guiding for a cooler third quarter for their trading desks, weighed down in part by their fixed-income trading businesses. Markets saw a turbulent summer: the AI trade stumbled as semiconductor stocks fell, hedge fund Situational Awareness suffered a bruising decline and leveraged investors unwound their riskiest positions. Stocks subsequently recovered, and the S&P 500 ended the quarter with a gain.

The end result for banks is likely to be of the best third quarters they've had, better than a year ago, but not as strong as that second-quarter bonanza.

"I think it's safe to say, 3Q is no 2Q," Morgan Stanley's Co-President Dan Simkowitz said at an industry conference hosted by Barclays in September.

Bank stocks have also pulled back in the past month, hurt by concerns about the Federal Reserve raising interest rates, rising AI uncertainty and the threat that the new technology poses to their own operations.

JPMorgan Chase Co-President Doug Petno said the bank is projecting its markets revenue to grow in the "mid- to high-teens" compared with the year-ago quarter, calling it "a very strong quarter."

Citigroup's finance chief Gonzalo Luchetti said the bank expects mid-single-digit revenue growth in its markets business for the quarter. And Bank of America Chief Executive Brian Moynihan said trading revenue will be "relatively flat" compared with the year before but "it'll be one of the better third quarters we've ever had."

Goldman Sachs CEO David Solomon said the equities business "continues to be very strong," while the fixed income, currencies and commodities business was softer.

The executives made their comments just as bond yields rose and investors refocused on global debt concerns, sending prices down.

Barclays analyst Jason Goldberg said he doesn't expect recent moves in the bond market to meaningfully impact the quarter, and that fixed-income revenue should be better than a year ago.

"I think it'll be a very strong quarter for equity trading revenues," Goldberg said. "It will still be the best third quarter ever for our coverage in terms of overall trading revenues."

Wall Street's largest banks are due to report third-quarter earnings the week of Oct. 12. Analysts polled by FactSet expect the five biggest Wall Street banks' per-share earnings to grow by an average of 20% from the same period a year ago.

Investment bank Jefferies on Monday reported capital markets revenue of $802 million for the quarter ending Aug. 31, up 11% from the year-ago quarter. Equities revenue grew 29%, reaching a record high, while fixed-income revenue fell 26%.

Morgan Stanley analyst Manan Gosalia said that while softer deal activity, additional Fed rate increases and talk of slowing the AI build-out weakened the near-term outlook for capital markets activity, the banks' fundamentals remain strong.

"We expect banks to highlight strong pipelines at earnings," Gosalia said.