Coinbase Says Altcoin Season Could Arrive in September—Here’s Why
Coinbase Institutional’s latest research, led by Global Head of Research David Duong, predicts a potential “full-scale altcoin season” by September 2025, inspired by the declining Bitcoin dominance and fast-changing market dynamics.
Bitcoin’s market share dropped from 65.4% in May to 58.63% as of Aug. 15, 2025, according to CoinCodex, an indicator of capital flowing into altcoins.
BTC Dominance (Source: CoinCodex)
The altcoin market capitalization, excluding Bitcoin, has risen approximately 40-50% since July to an estimated $1.6 trillion, based on CoinMarketCap data and industry estimates. Major altcoins are driving this trend: Ethereum reached $4,779 with an 18% weekly gain, XRP surpassed $3.10, and Solana hit $194.
The Altcoin Season Index, which tracks the top 50 altcoins’ performance against Bitcoin over 90 days, increased from 28 in July to 45 as of Aug. 15, 2025, approaching 50. While still under the 75 threshold of a true altseason, the upward trend suggests growing momentum.
Altcoin Season Index Chart (Source: CoinMarketCap)
Historical patterns, especially following the April 2024 Bitcoin halving, support that prediction, as altcoin rallies historically start 480 days following the halving, which is around September 2025.
Economic Shifts and Regulatory Wins Set Stage for Altcoin Season
Coinbase links its bullish prediction to macroeconomic conditions.
The United States inflation was 2.7% year-over-year in July, with futures markets predicting a 92% chance of a Federal Reserve rate cut in September. This could redirect capital from $7.2 trillion in United States money market funds to riskier assets like altcoins as yields on traditional investments decline.
Stablecoin adoption and institutional investor interest in Ethereum are also drivers behind the rotation, with Ethereum’s staking and decentralized finance, or DeFi, use cases attracting major inflows.
Regulatory developments also support the altcoin narrative. Bipartisan legislation, including the FIT21, GENIUS, STABLE, and CLARITY Acts, is advancing in Congress, potentially clarifying regulatory frameworks and encouraging institutional involvement.
The SEC is reviewing multiple crypto ETF proposals, including those for Solana and XRP, which could improve altcoin credibility.
Growing sectors like real-world asset (RWA) tokenization and DeFi, with a 6.2% increase in total value locked in Q2 2025, are shaping the next market cycle.
However, analysts note that the absence of a dominant primary-market catalyst, in comparison to previous ICO or NFT booms, may slow the rally’s pace.
What Investors and Experts Are Saying
Market sentiment across communities and social media remains positive in expectation of an altcoin season, with community members pointing to Bitcoin dominance falling below 60% and August-September pumps in past years.
Analysts cite Ethereum’s outperformance and technical breakouts in altcoins like Flare and Drift as early indicators.
Sectors such as AI, DeFi, and meme coins are gaining attention, with low-cap tokens attracting speculative interest, in line with post-halving cycle patterns.
Kaiko Research warns that liquidity concentration in major altcoins like Ethereum may affect the overall market gains and favor only projects with strong fundamentals.
