Bitcoin’s September curse: Why history says BTC could crash 30% next month

Key takeaways

September has often been a bad month for Bitcoin, with losses in eight of the last 11 years. Right now, traders seem unsure, and if fear takes over, Bitcoin could fall again — possibly by as much as 30%.

September has rarely been kind to Bitcoin [BTC].

BTC has historically posted negative returns during this month, and 2025 might be no different. With caution on the horizon, BTC could drop as much as 30% if past patterns play out again.

September: A Bitcoiner’s heartbreak

Since 2013, BTC has posted negative returns in eight out of 11 Septembers, with an average drop of 3.77% and a median fall of 4.35%.

The worst September came in 2014, when BTC tanked nearly 19%, followed by 13.38% in 2019 and 13.88% in 2022.

Source: CoinGlass

Even in bull market years like 2017 and 2021, September delivered losses of 7.44% and 7.03% respectively. This recurring pattern may be a seasonal trend of profit-taking or cautious investor behavior.

With BTC already facing resistance, a repeat of history could mean further downside ahead.

Bitcoin leverage high, but conviction isn’t

Despite Bitcoin’s recent dip, aggregated Open Interest remains elevated at over $39.5 billion; traders are still heavily exposed to the market.

However, the Funding Rate average is only slightly positive (0.0046) – a sign of weak directional bias. While positions are loaded, traders are hesitant to go aggressively long or short.

Source: Coinalyze

Typically, high Open Interest combined with flat funding rates can be a sign of indecision or a buildup to volatility. If sentiment flips bearishly (as September often triggers) this leveraged stack could unravel fast.

Bitcoin momentum builds, but will it be enough?

Bitcoin spot ETFs saw mixed flows in August, with BlackRock’s IBIT pulling in $114.4 million even as total net outflows touched $17.67 million for the month.

Source: SoSoValue

This contrasts with the strong ETF inflows seen from April to July. Monthly net inflows steadily grew alongside BTC’s price and total net assets swelling past $151 billion.

Ethereum [ETH], meanwhile, dominated inflows in August, drawing five times more capital.

Yet, institutional confidence in BTC remains strong. Brevan Howard committed $2.3 billion to BlackRock’s ETF, and Dutch firm Amdax is launching a Bitcoin treasury vehicle aiming to secure 1% of BTC’s supply.

September has a shot at breaking its losing streak… if inflow momentum deepens.