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Ethereum’s rally this month has been sharp, but traders are being warned to watch September closely.
Ether climbed about 20% since the start of August, trading at $4,745 at the time of publication. Prices even pierced $4,860 after dovish remarks from US Federal Reserve Chair Jerome Powell at the Jackson Hole symposium, a move that many in crypto see as a possible spark for more gains.
Historic September Pullbacks
According to CoinGlass, history offers a cautionary note: there have been only three cases since 2016 where Ether rose in August and then slid in September.
In 2017, Ether jumped 92% in August and then dropped 20% the following month. In 2020, August gains of 25% were followed by a 17% pullback in September.
And in 2021, a 35% climb in August gave way to a 12% slip in September. CryptoGoos, a trader on X, summed it up bluntly: seasonality in September during post-halving years tends to be negative.
$ETH seasonality in September during post-halving years is typically negative.
Will this time be different? pic.twitter.com/h9hJ40V3np
— CryptoGoos (@crypto_goos) August 22, 2025
That pattern does not mean a repeat is guaranteed. Reports have disclosed that both market structure and investor profiles are different now than in those earlier years.
In 2016 and 2020, short-term losses in September were followed by multi-month recoveries, with Ether posting upside in the final three months of those years. So while history matters, it does not decide outcomes on its own.
New Money, New Dynamics
Flows into spot Ether ETFs this month have been large enough to grab attention. Based on reports from Farside, spot Ether ETFs saw roughly $2.70 billion net inflows in August, while spot Bitcoin ETFs experienced about $1.2 billion in net outflows over the same period.
At the same time, companies that hold crypto on their balance sheets now control a sizable chunk of Ether. Reports show total Ether held by treasury companies topped $13 billion in value on Aug. 11.
Arkham reported that BitMine chairman Tom Lee bought another $45 million of Ether, lifting BitMine’s stack to $7 billion.
Those numbers change the math. Big institutional stacks and ETF demand can make sharp, short-term moves more persistent than in prior cycles.
Capital appears to be rotating; Bitcoin dominance has fallen 5% over the past 30 days to 55%, which market participants mostly attribute to funds moving into assets beyond Bitcoin.
What Traders Might Do Next
Traders and portfolio managers will likely keep an eye on macro signals and flow data. A softer interest rate outlook from Powell is a bullish factor for risk assets, but seasonality and previous post-August declines are reasons to stay cautious.
Featured image from Unsplash, chart from TradingView
