For more than a decade, September has been the bogey month for digital assets. Year after year, Bitcoin and Ethereum have struggled through the month, weighed down by seasonal selling pressure, weak liquidity, and nervous investor sentiment. Yet, in 2025, the backdrop looks significantly different. With thinner exchange reserves, institutional accumulation, and exchange-traded funds (ETFs) acting as structural buyers, could this September finally defy history?

A History of September Blues

The idea of “crypto September blues” is not just folklore, it is supported by hard numbers. Since 2013, Bitcoin has posted a median September return of –3.1%, while Ethereum, which joined the market later, has averaged an even worse –12.7%.

The declines have often been sharp and memorable:

• 2014: Bitcoin crashed –19%.

• 2015: Ethereum plunged –45% in its worst September on record.

• 2017: Ethereum fell –21% amid one of its most volatile years.

• 2019: Bitcoin lost –14% while Ethereum managed a modest +3.95%.

• 2022: tightening liquidity dragged BTC down –3.1% and ETH by –14.6%.

Bitcoin Price History: Cryptorank

Even in bullish years, September tended to undercut momentum, halting rallies in their tracks. The pattern created a reputation that stuck.

But in September 2024, the trend bent, if not fully broke. Bitcoin gained 7.1%, while Ethereum rose 3.2%, supported by ETF launches and a 50-basis-point Fed rate cut. That shift raised the prospect that the “curse” could fade under new market structures.

Exchange Reserves Thinner Than Ever

One of the clearest structural changes heading into September 2025 is the sharp decline in exchange reserves. Historically, high balances on exchanges meant that a large supply was available to sell quickly, fuelling drawdowns.

BTC Exchange Reserves: CryptoQuant

This year, the picture is different:

• Bitcoin reserves: down from about 3.0 million BTC in September 2024 to 2.4 million BTC today.

• Ethereum reserves: down from 19.3 million ETH to 17.3 million ETH.

With less coin sitting idly on exchanges, the potential for panic selling has thinned. On top of this, data suggests that whales have already begun September accumulation, a stark contrast to previous years when the month started with net outflows.

ETFs as a Structural Buying Force

The most important difference between this cycle and earlier ones is the presence of spot ETFs. Inflows have been steady and material, creating a new floor of demand that cushions volatility.

• Bitcoin ETFs: lifetime inflows have crossed $54.58 billion, with $332.76 million added already in September 2025.

• Ethereum ETFs: lifetime inflows now stand at $13.49 billion.

ETH ETF Stash: SoSo Value

Unlike the speculative flows of retail traders in past Septembers, ETF demand is institutional, sticky, and often agnostic to short-term price moves. In earlier cycles, no such mechanism existed to absorb selling pressure.

Stablecoins and Institutions Add Firepower

Alongside ETFs, the stablecoin market has doubled in strength over the past year.

• Stablecoin reserves on 4 September 2024: $28.4 billion.

• Stablecoin reserves on 4 September 2025: $54.9 billion.

This pool of liquidity represents “dry powder” capital already sitting on-chain that can be quickly deployed on dips. This is another reason why the dynamics of September 2025 differ sharply from previous years.

At the same time, institutional treasuries are active buyers. The top 100 public companies holding Bitcoin collectively own 998,613 BTC, while Ethereum has begun to see institutional attention as well. Sharplink Gaming, for instance, disclosed holdings of 837,230 ETH as of August 31. Other companies, such as Bitmine, continue to accumulate.

This trend is crucial: historically, only Bitcoin had a strong institutional following, while Ethereum was left more vulnerable in September downturns. That imbalance is fading in 2025.

Risks That Could Keep the Curse Alive

Despite the stronger structural backdrop, September still carries its risks.

BTC Supply In Profit Percentage: Glassnode

Both BTC and ETH are near all-time highs, meaning the majority of holders are sitting on significant gains.

• Bitcoin in profit: up from 73.8% in Sept 2024 to 90.1% today.

• Ethereum in profit: up from 69.9% to 95.9%.

High levels of profitability create natural incentives for profit-taking, especially in a month already associated with weak seasonality.

Withdrawal Address Weakness

The number of unique Bitcoin withdrawal addresses, a proxy for conviction in self-custody has declined from 37,745 in Sept 2024 to 15,241 today. This suggests softer conviction among retail and smaller investors.

However, the figure spiked to 62,977 on 3 September, showing that buying interest does return on dips. With reserves lower than in the past, the risk from reduced withdrawals is less damaging, though still worth monitoring.

Macro Headwinds

The U.S. 10-year Treasury yield at 4.22% signals tight liquidity and a preference for safer assets. Gold trading at record highs underscores that investors remain risk-averse.

Analysts at Bitfinex, speaking on 2 September, warned that macro jitters could drive near-term weakness:

“Major cryptocurrency assets endured a difficult week as macro jitters and the post-PPI sell-off weighed heavily on price action. BTC is now down over 13 percent from its recent all-time highs, and while trading below the January peak is not an encouraging signal, we believe the market is nearing the bottom of this downturn as we move into September.”

The silver lining is that the Federal Reserve is expected to cut rates again this month, a tailwind similar to the one that buoyed September 2024.

Could This Be the September That Breaks the Curse?

For more than a decade, September has been synonymous with crypto drawdowns. But 2025 brings an entirely new set of conditions:

• Exchange reserves at multiyear lows.

• ETF demand exceeding $68 billion.

• Stablecoin firepower doubled.

• Institutions actively buying dips.

Yes, risks remain. High profit supply and elevated yields could still trigger bouts of volatility. Yet, the difference this year is the strength of mitigating forces from ETFs to corporate treasuries, that were largely absent in earlier cycles.

If Bitcoin and Ethereum manage to not only hold ground but also push to new all-time highs this month, the irony would be historic. September, once the darkest month in crypto’s calendar, could become the one that marks the true beginning of a new cycle.