Bitcoin has historically struggled in September, posting six consecutive negative monthly returns from 2017 through 2022. However, the pattern has weakened considerably in recent years, with positive September closes recorded in 2023, 2024, and 2025.
The seasonal weakness is not unique to Bitcoin. The S&P 500 has averaged around -0.8% in September over the last 50 years, suggesting broader market seasonality effects.
Recent Performance Shifts the Outlook
Bitcoin gained approximately 25.6% in August 2026, pushing prices back toward the $80,000 level and breaking a historically weak trend for that month. This rally broke long-standing resistance levels and has generated market interest heading into September.
Several on-chain metrics suggest improved conditions. Bitcoin's SOPR (Spent Output Profit Ratio) moved above 1.0 by late August, indicating holders were increasingly willing to sell at a profit. The Mean Coin Age rose above 1.70K, suggesting a growing portion of Bitcoin's supply remained unmoved rather than actively traded.
The Coinbase Premium Index recovered to 0.00 after remaining negative for 14 consecutive days, reaching a neutral point after a period of selling pressure.
Strength of Seasonal Pattern Uncertain
According to CryptoQuant, September could be challenging for both U.S. stocks and Bitcoin in 2026. However, historical seasonality patterns do not guarantee outcomes in individual years.
With strong spot and ETF demand, analysts suggest the September weakness pattern could fail to materialize again in 2026, continuing the reversal of the seasonal trend observed in recent years.
