September 2025 Market Seasonality – S&P 500, Nasdaq 100 Vulnerable to Seasonal Dip
September Seasonality Key Talking Points:
- Historically, September has been the weakest month for US stocks, with the broad S&P 500 index sporting an average (price-only) return of -0.8% over the last 35 years.
- September has historically been the month where stock market volatility rises the most, with the VIX index rising by an average of 8.2% since 1990.
- Gold and WTI Crude Oil have also shown bullish seasonal tendencies in September.
The beginning of a new month marks a good opportunity to review the seasonal patterns that have influenced the markets since 1990.
As always, these seasonal tendencies are just historical averages, and any individual month or year may vary from the historic average, so it’s important to complement these seasonal leans with alternative forms of analysis to create a long-term successful trading strategy. In other words, past performance is not necessarily indicative of future results.
S&P 500 Seasonality – S&P 500 (Price-Only)
Chart Source: TradingView, StoneX.Please note that past performance is not necessarily indicative of future results.
Historically, September has been the WEAKEST month for US stocks, with the broad S&P 500 index sporting an average (price-only) return of -0.8% over the last 35 years. As of writing, the index has gotten off to a rough start, falling sharply on the first trading day of the month amidst fears of rising yields, though hopes of imminent rate cuts from the Federal Reserve could limit the downside somewhat as we move through September. The S&P 500 did buck the weak seasonal trend in August, but after four straight “up” months, some give back in an historically weak month would not be surprising.
Nasdaq 100 Seasonality – NDX (Price-Only)
Chart Source: TradingView, StoneX. Please note that past performance is not necessarily indicative of future results.
Looking at the above chart, the Nasdaq 100 has historically seen its weakest performance in September as well, to the tune of -0.6% since 1990. Like the S&P 500, the Nasdaq 100 rallied to record highs in August before pulling back in the latter half of the month and threatening to break its 4-month bullish channel as we go to press. Traders should keep a close eye on Nvidia’s performance in particular, with the AI behemoth falling to 5-week lows after a mixed earnings report in late August.
Volatility Index Seasonality – VIX
Chart Source: TradingView, StoneX. Please note that past performance is not necessarily indicative of future results.
September has historically been a month where stock market volatility rises, with the VIX index rising by an average of 8.2% since 1990, essentially tying its biggest up month. The VIX bucked its seasonal trend in August, edging down to close near 15 after spiking above 20 earlier in the month. For volatility traders (or any readers trading markets in general), the coming month should be particularly interesting, as traditional volatility catalysts from earlier in the year (US fiscal stimulus, trade policies, and geopolitical tensions) have simmered down, but the seasonal trend nonetheless points to potential upside.
Gold Seasonality – XAU/USD
Chart Source: TradingView, StoneX. Please note that past performance is not necessarily indicative of future results.
Turning our attention to commodities, September has historically been a bullish month for gold performance, with an average rise of 1.0% going back to 1990, the precious metal’s second-strongest month of the year. After consolidating for the last five months, gold is breaking out to record highs above $3500 to start September, setting the stage to extend its historic rally amidst still-falling interest rates globally, trade uncertainty, and a well-established uptrend going back to late 2022, and the seasonal trend aligns with those bullish fundamental factors, along with the technical breakout.
WTI Crude Oil Seasonality – WTI Chart
Source: TradingView, StoneX. Please note that past performance is not necessarily indicative of future results.
Last but not least, WTI Crude Oil has historically gained ground in September, with an average gain of +2.1% over the last 35 years. WTI rose in fell in August, remaining below a nearly 2-year bearish trend line. That said, the trend line sits up above $70, leaving room for a meaningful monthly rally if the seasonality holds before encountering resistance. A confirmed break above that barrier in the $73 area would be needed to shift the longer-term trend back in favor of the bulls, while the downside level to watch is near last month’s low in the $62 range.
As always, we want to close this article by reminding readers that seasonal tendencies are not gospel so it’s important to complement this analysis with an examination of the current fundamental and technical backdrops for the major markets and the global economy.
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-- Written by: Matt Weller, Global Head of Research
