Analysis of September seasonality in Bitcoin and stock markets, exploring the 'Red September' phenomenon and historical performance patterns.
Macro & Markets ·
Bitcoin has closed lower in eight of its last 13 Septembers, posting an average decline of 2.97% and marking the weakest month on its calendar. The stock market shares this affliction—the S&P 500 has posted negative average returns in September since 1945, with researchers tracing the pattern back to 1928. The phenomenon, known as "Red September," extends beyond superstition: June is the only other month approaching this loss rate, while October averages a 19.92% gain.
The mechanics remain debated. Traditional explanations for equities include fiscal-year rebalancing by mutual funds harvesting tax losses on October 31 deadlines, institutional desks resuming activity after summer breaks and executing deferred risk reductions, and Federal Reserve mid-month meetings coinciding with market volatility. Bitcoin lacks these institutional rhythms yet mirrors the pattern, suggesting a broader financial correlation. Additionally, 2026 arrives as a midterm election year; across the prior ten midterm cycles since 1986, average stock market lows have landed on September 2 with drawdowns near 17%.
Last year's September initially tracked the seasonal script before reversing course, delivering a 5.16% gain and marking Bitcoin's third consecutive green month. What sparked the reversal and whether such breaks can recur remains uncertain, especially as Bitcoin opens the current September around $77,500 following a near 25% August rally.