US stocks and cryptocurrencies begin September facing their weakest month on record. The S&P 500 closed August with gains of more than 2% and set record highs along the way.

Bitcoin (BTC) and Ethereum (ETH) also finished the month strongly, gaining 24.95% and 32.5%. Historical data now points to a tougher stretch for both markets.

Stocks Carry a Long September Losing Record

The Dow Jones Industrial Average has fallen an average of 0.8% in September since 1950, according to the 2026 Stock Trader’s Almanac. The S&P 500 has shed 0.7% over the same span.

The Nasdaq Composite has dropped 0.9% since 1971, and the small-cap Russell 2000 has lost 0.8% since 1979. Bank of America data dating back to 1928 show an average September S&P 500 loss of 1.17%, with the index falling in 56% of those years.

Almanac authors Jeffrey Hirsch and Christopher Mistal tie the pattern to fund behavior after the summer break.

“Portfolio managers back after Labor Day tend to clean house in September,” they said.

This follows a strong August for stocks. The S&P 500 rose more than 2% and closed at a record 7,798.99 on August 13, its 27th record close of 2026. The Dow added over 1%.

Corporate earnings drove the run. Pre-tax profits reached $4.8 trillion in the second quarter, the highest share since at least 1950.

Several pressures now sit against that backdrop. The United States and Iran exchanged strikes for the first time in over a month. July personal consumption expenditures inflation ran at 3.7%, nearly double the Federal Reserve’s 2% target. 

JC O’Hara, chief technical strategist at Roth, wrote that midterm election years have historically produced volatility in September and October.

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Crypto Faces the Same Calendar Problem

Digital assets carry a matching seasonality record. Bitcoin has averaged a 2.87% decline in September since 2013, its weakest month, with a median loss of 2.44%, per Coinglass.

Ethereum shows a wider gap. The asset has averaged a 9.40% September drop since 2015, with a median decline of 9.14%, according to CryptoRank.

However, the recent record complicates the pattern. BTC closed higher in each of the past three Septembers, gaining 5.16% in 2025 and 7.29% in 2024. ETH rose 3.20% in September 2024.

Both assets also enter the month with momentum. BTC gained 24.95% in August, while ETH advanced 32.5%.

Equity seasonality has softened in a similar way. The S&P 500 rose 2.02% in September 2024 and 3.5% in 2025, back-to-back gains that cut against the long-run average. 

This year, the calendar test arrives alongside midterm elections, inflation above target, and surging crude prices.

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Source: BeInCrypto