September has a strange reputation in markets. Historically, it has been the most volatile month of the year, yet betting on the VIX to rise has been no more reliable than flipping a coin.
The Cboe Volatility Index, the market’s main gauge of expected S&P 500 swings, has gained an average of 8.2% in September since 1990, according to TradingView data.
That is the strongest monthly average on the calendar, ahead of August and February. But the VIX has finished higher in only 18 of 36 Septembers.
Yet, something remarkable has happened over the past five Septembers.
Five Septembers: Five VIX Gains
The VIX has risen in each of the past five Septembers (a five-year winning streak):
- 40.27% in September 2021
- 22.24% in 2022
- 29.13% in 2023
- 11.96% in 2024 and
- 6.12% in 2025.
This is not the first time September has produced one. The VIX rose for five consecutive Septembers from 1991 through 1995. It did the same again from 1999 through 2003.
Both streaks stopped at five.
Since 1990, the VIX has never posted gains in six consecutive Septembers. With the index trading near 16 at the start of September, this month offers another test of that unusual seasonal pattern.
Can the streak finally reach six?
Extreme Events Are Likely Responsible
The 8.16% average September gain does not mean volatility normally jumps 8% during the month.
In September 2008, during the global financial crisis, the VIX surged 90.75%. It was the third-largest monthly VIX increase since 1990.
Only August 2015, when the VIX jumped 134.57%, and February 2020, when it surged 112.90%, were larger.
This is why the September volatility trade needs to be handled carefully.
The historical signal is not that the VIX usually explodes; It is that September has produced unusually large volatility shocks when markets become stressed.
Is Wall Street Watching the Risk?
In an August note, Bank of America technical strategist Paul Ciana said, “With volatility near cycle lows and seasonal risks rising in the August-October months, current levels may offer opportunity to add protection.”
That matters because volatility itself is currently subdued.
When volatility is low, investors can potentially buy downside protection at a lower cost. If markets suddenly become unsettled, that protection can become more valuable.
Ciana is not predicting a September selloff. Instead, he is highlighting a mismatch between low current volatility and a seasonally riskier period.
And this year, there is another reason to watch the calendar.
The Fed Meeting Lands In The Middle Of It
This year, a major market event falls almost exactly inside the historical September risk window.
The Federal Open Market Committee meets Sept. 15–16 and will release a new Summary of Economic Projections.
The projections will provide investors with fresh forecasts for economic growth, unemployment, inflation, and interest rates. The September update also extends the forecast horizon, bringing 2029 into view for the first time.
That gives markets another potential source of volatility.
VIX exposure can be tracked by the ProShares VIX Short-Term Futures ETF (BATS:VIXY), which rolls into pricier contracts every month and bleeds value whenever markets remain calm.
The question is no longer simply whether September will be volatile. It is whether a historically volatile month, a five-year VIX winning streak and a major Federal Reserve meeting will collide at the same time.
For investors, that may be the more interesting September trade.
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