Bitcoin investors have lost money in eight of the last 13 Septembers, with the digital asset averaging a 2.97% decline in the month—the worst performer on the calendar. This seasonal weakness isn't unique to crypto. The S&P 500 has averaged a 0.6% decline in September since 1945, the only month with a negative long-run average, a pattern researchers have traced back to 1928.
The consistency of September weakness defies easy explanation. For stocks, leading theories include mutual funds harvesting tax losses before their October 31 fiscal year-end, institutional traders executing deferred de-risking after summer breaks, and Fed policy meetings landing during market volatility. Bitcoin lacks these institutional rhythms but still follows the pattern.
Since 2013, Bitcoin closed September lower 38.5% of the time, with a negative median return of 2.44%. June is the only other month approaching similar weakness, averaging a 1.59% loss. October by contrast has returned 19.92% on average.
This year adds complexity. 2026 is a midterm election year, and across the last 10 midterm cycles since 1986, average stock market lows have landed on September 2, with drawdowns averaging nearly 17% from prior highs before recovery. Bitcoin now trades with high correlation to tech stocks, meaning electoral-year seasonality could apply.
Bitcoin opened September 2026 near $77,500 following a 25% August rally. The Federal Reserve is weighing its first rate hike since 2023, with the CME FedWatch tool putting odds of a September rate hike at 68.2%. Gold has rallied alongside Bitcoin, suggesting investors are hedging against continued inflation rather than seeking risk exposure.
Last September initially appeared to confirm the curse, with Bitcoin briefly touching $111,986 by mid-month after $162 billion was wiped from crypto's total market cap. The month recovered to close up 5.16%, marking the third consecutive green September on record. The reprieve was brief. October turned negative for the first time since 2018, closing down 3.69% after a Trump tariff threat triggered $19 billion in liquidations and the forced exit of 1.6 million traders.
