While Bitcoin has been trending sideways in the last days of August, cryptocurrency investors are preparing for the possibility of an impending decline, as they do every year during this period.
This phenomenon, known in the market as “Red September” or the “September Effect,” has been observed in traditional markets for nearly a century.
Since 1928, the S&P 500 index has recorded an average negative return in September, making it the only consistently negative month in the index’s history. The picture is even bleaker for Bitcoin: since 2013, Bitcoin has lost an average of 3.77% of its value in September, experiencing eight sharp declines, according to Coinglass data.
FinchTrade consultant Yuri Berg explains this as follows:
“September has become more of a psychological experiment than a market anomaly. A selling wave is being generated by expectations rather than historical data.”
This phenomenon stems from structural market behavior. Many investment funds close their fiscal year in September, divesting losing positions for tax reasons, and rebalancing their portfolios. With the summer holidays over, investors return to their trading desks to review their positions after a period of low liquidity. Furthermore, increased bond issuance after September accelerates the exit from stocks and risky assets.
On the crypto side, these effects are even more magnified. Bitcoin, which trades 24/7, lacks circuit breakers during sell-offs, and its smaller market cap makes it vulnerable to large investor movements.
September 2025 is approaching with mixed signals. The Fed has delivered positive messages, with markets pricing in the possibility of another interest rate cut for its September 18 meeting. Meanwhile, core inflation remains resilient at 3.1%, while two active wars are disrupting global supply chains.
InFlux Technologies CEO Daniel Keller describes this scenario as a “perfect storm”:
“There are two major conflict zones in Europe and the Middle East, affecting critical supply chains. Furthermore, the US has entered a trade war with many of its allies. This geopolitical environment increases the risk of a significant decline for Bitcoin in September.”
However, DYOR CEO Ben Kurland thinks differently:
“’Red September’ is more of a myth. Historically, September has looked weak because of portfolio rebalancing, waning retail investor interest, and macro uncertainties. But that was true when Bitcoin was smaller. Today, liquidity is the real determining factor.”
Keller advises investors to closely monitor fear and greed indices:
“Gauge market sentiment in the coming weeks is critical. If the indices rise, it may be necessary to wait; if they fall, it may be necessary to prepare for selling.”
*This is not investment advice.
