September enters with reputation as Wall Street's weakest month

Adds new blog entry

Indexes fall, Nasdaq leads losses with >1% drop

Energy leads S&P 500 sector gainers, consumer discretionary lags most

STOXX 600 down ~0.3%

Dollar rises, US crude up ~3%, gold falls >2%, bitcoin off >1%

US 10-year Treasury yields rise to ~4.77%

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Welcome to September, historically the weakest month of the year for U.S. stocks.

The month’s reputation is backed by more than a century of market data. Since 1920, U.S. equities have risen in September only 44% of the time and posted an average loss of 1.1%, according to a SentimenTrader analysis by Jay Kaeppel.

By comparison, stocks gained in 60% of the 1,173 non-September months between 1920 and 2025, with an average return of 0.8%, Kaeppel said.

September’s seasonal weakness has been even more pronounced during U.S. midterm election years, potentially adding to investor caution as markets enter September 2026. Five of the S&P 500’s nine September declines of 9% or more occurred during midterm years, according to Kaeppel.

Still, investors should not assume stocks are destined to fall this month, even if history argues for caution, he said.

“Longer-term investors who are considering hedging their portfolio should look to do so in the first few days of the month. Shorter-term traders looking to play the short side should be ready to act if the market starts to show weakness, particularly as the month progresses,” he said.