Everything on Market Seasonality

September is statistically the weakest month for equity markets, driven by options expiration, tax harvesting, and post-summer risk aversion. The S&P 500 has averaged a -0.6% return in September, with the worst historical drop occurring in 1939.

Impact: Investors should anticipate higher volatility and potential drawdowns in September, using the period to rebalance portfolios or accumulate quality assets at lower prices.

— from September Market Dynamics: Defense, ETFs, and Solar · Deffner und Zschäpitz – Der Wirtschafts-Talk von WELT· Sep 01, 2026