September’s bad reputation is built on the wrong sample. The standard line, that it is the worst month of the year for the S&P 500, is accurate when you throw every September since 1950 into one bin and take the average. But that average is not 2026’s base rate. Strip it down to years when August closed higher and the index entered September up between 10% and 17.5% for the year, and the picture changes: September has averaged a gain of 1.0%, with the final four months of the calendar finishing higher in 10 of 11 instances at an average of 5.6%, according to Carson Group’s Ryan Detrick.
The S&P 500 has gained about 13.1% year to date. Both conditions for that favorable subset are satisfied. Historical data stretching back to World War II reveals that when the S&P 500 achieves a positive August alongside year-to-date gains between 10% and 17.5% — conditions that match 2026’s year-to-date return — September itself averages a 1.0% gain.
The midterm overlay adds another wrinkle that most seasonal write-ups miss. “The four best September returns ever all took place in a midterm year and five of the top seven,” according to Detrick. In a midterm year, September ranks as the 10th worst month, with only January and June performing worse. That is a different animal from the month-is-cursed story that circulates every August 31.
None of that makes the next 16 sessions easy. The calendar has handed traders three events that will matter far more than the month on the page.
Three Catalysts That Actually Drive the action in September
1. Friday’s payroll report. The August jobs report arrives Friday, September 4, closing out a week that also delivers ISM manufacturing and services surveys, the JOLTS openings data, the ADP employment reading, and the Federal Reserve’s Beige Book. The prior month’s read was deeply negative: the BLS reported July 2026 nonfarm payroll employment changed little at negative 23,000, with the unemployment rate holding at 4.1%. A second consecutive weak number could flip the Fed calculus quickly.
2. The September 15-16 FOMC meeting. The yield on the 10-year Treasury note traded around 4.75% at the end of August. In his Jackson Hole remarks on August 28, Federal Reserve Chair Kevin Warsh said inflation is still too high and signaled that rate hikes may be needed in the months ahead to bring it down. A hike in September would be an escalation in a cycle that has already included cuts, and it would land with the S&P 500 near all-time highs.
3. Crude oil and the Strait of Hormuz. Brent traded around $91.23 a barrel on September 1. July personal consumption expenditures inflation ran at 3.7%, well above the Federal Reserve’s 2% target. Sustained crude above $90 keeps that pressure alive and gives Warsh cover to stay hawkish.
The Technical Picture and What to Watch
The VIX closed at 15.02 at August’s end. The VIX has historically started climbing around this time of year, with its median level since 1990 sitting around 16.5 in late August, rising toward 18 by mid-September, and reaching roughly 19 in early October. Cheap volatility is not a green light. It means risk is being priced low into a period with genuine binary outcomes on rates.
Ryan Detrick has identified 7,610 as a key support level to monitor. The second half of September deserves particular attention given its historically weak record, and traders should watch whether market breadth deteriorates, volatility rises, or major indexes begin losing key technical support.
The seasonal argument for caution is real but overused. The argument for blind optimism is equally sloppy. What matters in the next 16 sessions is whether Friday’s payrolls give the Fed a reason to pause, whether Warsh tightens policy into a slowing labor market on September 16, and whether Hormuz tensions cool or escalate further. Those three developments, not the name of the month, will set the tone for SPY, VOO, and IVV through the end of the quarter.