Altcoin season could be on the horizon as momentum shifts across the crypto market. Bitcoin dominance fell sharply from over 65% to 63.89%, just as BTC broke past $100,000 for the first time since February 3. This triggered a broad altcoin rally, with Ethereum up nearly 13% and major names like SOL, DOGE, and ADA each gaining more than 6%. Combined with a bounce in the ETH/BTC ratio from its lowest levels since 2020, the setup suggests a possible rotation into altcoins for the first time in months. Altcoin Season Incoming? Bitcoin Dominance Dips as ETH and Majors Surge Bitcoin dominance dropped sharply from over 65% to 63.89% in just a few hours after BTC surged past $100,000 for the first time since February 3. This shift has sparked a strong altcoin rally, with Ethereum jumping nearly 13% in the last 24 hours, while Solana (SOL), Dogecoin (DOGE), and Cardano (ADA) each gained more than 6%. BTC Dominance (%). Source: TradingView. Until yesterday, Bitcoin dominance was at its highest level since January 2021, showing how aggressively BTC outperformed the broader market in recent months. A sudden reversal like this often signals a capital rotation, with traders beginning to shift profits from BTC into altcoins. Recently, CryptoQuant CEO Ki Young Ju called Bitcoin Cycle Theory obsolete as TradFi takes over. Adding to this narrative is the ETH/BTC ratio, which recently hit its lowest level since 2020—marking an extended Ethereum underperformance relative to Bitcoin. ETH/BTC Ratio. Source: TradingView. A bounce from such historical lows could indicate the start of a structural shift favoring altcoins. If BTC dominance continues to fall while ETH/BTC rises, it would be a strong signal that the market is transitioning into an altcoin season. With altcoin volumes rising and capital rotating into broader sectors, May 2025 could begin a major altcoin season. May 2025: A Turning Point Toward Altcoin Season? The CoinMarketCap Altcoin Season Index has surged from 23 to 36 in the last four days. This index tracks whether Bitcoin or altcoins outperform over a specific period. Readings below 25 indicate “Bitcoin Season,” where BTC outpaces most altcoins. Scores between 25 and 75 are considered neutral, while values above 75 officially signal “Altcoin Season.” CMC Altcoin Season Index. Source: CoinMarketCap. The current jump into neutral territory comes after reaching a yearly low of 12 in late April—its weakest point since December, when it peaked at 87. The CMC Altcoin Season Index measures whether at least 75% of the top 100 coins (excluding stablecoins and asset-backed tokens like WBTC and stETH) have outperformed Bitcoin over the last 90 days. Top 18 Biggest Coins (YTD Performance). Source: Messari. So far in 2025, Bitcoin is up 10% year-to-date—outperforming nearly all major altcoins except XRP, which has gained over 12%. Meanwhile, Ethereum remains down 30% YTD, and coins like LINK, DOGE, AVAX, and SHIB have all dropped more than 20%. Despite this weak YTD performance, the sharp drop in BTC dominance, strong altcoin rallies in early May, and the rising Altcoin Index all point to the possibility that May 2025 could begin a new altcoin season.