Before the first full week of September arrives, investors face a 72-hour sequence that would unsettle almost any month: Nvidia’s fiscal Q2 report lands after tonight’s close, July PCE hits Wednesday morning, and Fed Chair Kevin Warsh steps to his first Jackson Hole podium Friday at 10 a.m. ET. Nvidia’s earnings and the Fed’s biggest set-piece event land just 36 hours apart. That is an unusually compressed calendar, and it lands with the S&P 500 sitting at 7,677.28 after Tuesday’s 0.32% gain.
The predictable response is to reach for the September seasonality argument. Resist it.
What History Actually Says
From 1928 to 2025, the S&P 500 averaged a return of negative 1.13% in September, the lowest of any month, with February a distant second at negative 0.10%. No other month has averaged a negative return. That is a real pattern in the data. It is not, however, a reliable forecast for any individual September. Last September, the S&P 500 rose 3.5%.
More importantly, the mechanism behind September weakness is structural, not mysterious. Many mutual funds close their fiscal year in October, and institutional investors tend to clean up portfolios in September by selling their worst-performing stocks before that deadline. That behavior is well-documented and increasingly anticipated. Calendar effects are weaker today than the textbooks suggest, because algorithmic and quantitative strategies now account for a large share of market volume and arbitrage away simple, well-publicized calendar inefficiencies quickly.
Selling equities to sidestep a one-percentage-point average monthly drag, while forfeiting November and December’s historically strong returns, is a wealth-shrinking decision dressed up as prudence.
The Actual Risks Worth Watching
That said, this particular September opens with legitimate uncertainties that deserve attention, just not the ones driving calendar panic.
On the Fed, Warsh delivers his first keynote as Fed Chair on Friday, August 28, just three weeks before the September FOMC meeting, with markets recently pricing in roughly one-in-three odds of a rate hike. Roughly half of FOMC participants penciled in at least one hike for 2026 in the June Summary of Economic Projections, and three regional presidents dissented in favor of hikes at his second meeting in July, an unusually high level of dissent so early in a new chair’s tenure. The Fed currently holds at 3.5% to 3.75%. A hike would be the first in this cycle and would immediately compress valuations on long-duration assets.
Nvidia’s guide is the other live variable. Nvidia posted $81.6 billion in fiscal Q1 revenue, up 85% year over year, and the stock still fell the next session. Attention goes straight to the guide, and forward consensus puts fiscal Q2 revenue around $92 billion. A guide toward or above $100 billion, with data center growth holding near last quarter’s pace, is the version that finally rewards the stock. Miss that bar, and sentiment across the AI complex cools heading into a rate-decision month.
On the consumer side, the Conference Board’s Consumer Confidence Index slipped to 89.4 in August, its weakest reading since January, driven by a drop in the expectations component covering the six-month outlook for income, business, and labor market conditions. Dick’s Sporting Goods illustrated the pressure directly: shares closed at $124.31 on Tuesday, down more than 30%, after investors reacted to a Q2 earnings miss, lower full-year guidance, and weaker demand for athletic footwear and apparel. The newly acquired Foot Locker segment posted a comparable-sales decline of 3.6% and an operating loss of $31.9 million for the quarter. Consumer discretionary names carrying integration risk deserve extra scrutiny before the hike decision.
Two Adjustments Worth Making Now
The first is adding quality where valuations are compelling after recent dislocations. Moderna is a case in point. A personalized mRNA cancer vaccine, added to Keytruda, slowed the return of melanoma and its spread in a late-stage clinical trial, results that could herald a new approach in oncology. Leerink analyst Daina Graybosch estimates intismeran could reach average revenue of $1.4 billion by 2032. After years of post-pandemic disappointment, Moderna’s mRNA platform now has a phase 3 anchor in cancer. That changes the long-term risk calculus.
The second is reviewing interest-rate exposure across the portfolio. A hawkish Warsh speech would likely support the dollar and push Treasury yields higher, as investors would price in a better chance of the September hike. Bank of Montreal demonstrated what rate-sensitive financial strength looks like in a higher-for-longer environment: adjusted EPS came in at $3.96, up 22% year over year, with adjusted net income of $2.859 billion. Impaired provisions fell to their lowest level in 10 quarters. North American financials with clean credit books are a reasonable hedge against a hike that, if it arrives, will widen net interest margins further.
The Wealth Takeaway
September’s reputation is real but limited in its usefulness. What matters this year is not the calendar; it is whether Warsh signals a hike that the market is only halfway priced for, whether Nvidia’s Q2 guide confirms the AI buildout is intact, and whether consumer spending has genuinely softened or merely paused. Those are questions worth tracking. Selling simply because the month ends in “ber” is not a strategy. It is an emotion with a spreadsheet attached.
