September is historically the S&P 500’s weakest month. That is not a timing signal
The index has fallen an average of 1.1% in September since 1928, but the month has still produced gains in 44.5% of years.
September has historically been the S&P 500’s weakest calendar month, according to figures cited by Yahoo Finance from a republished Motley Fool article. Since 1928, the index has recorded an average September decline of 1.1% and finished the month higher in 44.5% of years.
The historical pattern does not establish that stocks will fall in any particular September. Avoiding the month could also leave investors on the sidelines during a positive period, while market timing requires getting both the sale and the subsequent purchase right.
The article points to the S&P 500’s history of recovering from corrections, bear markets, recessions, wars and financial crises. It argues that short-term weakness is generally less consequential for investors with long-term horizons than the cost of missing the market’s strongest sessions.
Fidelity figures cited in the article illustrate that risk. A $10,000 investment in the S&P 500 at the beginning of 1988 would have grown to roughly $616,000 by the end of 2025, compared with about $380,000 if the five best trading days had been missed.
The article’s guidance is to maintain regular investment schedules, including monthly purchases through 401(k) plans or other accounts, rather than attempt to forecast September’s result. The historical figures and Fidelity comparison are presented without underlying methodology in the supplied material, and the comparison is not a guarantee of future performance.
