In May 2025, over half of the top 100 altcoins briefly outperformed #Bitcoin — yet the broader market still refuses to call it “altseason.” In fact, the Altcoin Season Index has never crossed 31 this month, and after Bitcoin’s most recent drop, the gains made by many altcoins have already begun to fade.

So what happened? Did we just miss the altseason, or was it never really here?

Altcoins Surge in May — But Without Full Confirmation

Throughout the first half of May, market data confirmed that 57 out of the top 100 altcoins outperformed Bitcoin on a 30-day basis. Projects like AAVE, ARB, BGB, and XMR posted strong short-term gains, driven by ecosystem growth, L2 narratives, and DeFi utility.

But while these breakouts were real, they never translated into a synchronized market-wide altcoin rally. The Altcoin Season Index — which measures whether altcoins are outperforming $BTC across the top 50 tokens — peaked only at 31 and now sits at just 20, deep in Bitcoin dominance territory.

Not True Altseason — Just Temporary Rotation

This divergence tells a clear story: yes, altcoins saw stronger gains, but it wasn’t sustainable or broad enough to shift market structure.

In fact, as soon as Bitcoin dropped sharply over the weekend, many altcoins gave back a large part of their recent profits. The rally wasn’t invalidated entirely — but it was clearly shallow. Rather than signaling a true altcoin cycle, the data points to short-term risk-on behavior in pockets of the market.

And without a break above 75 on the Altcoin Season Index, the official definition of “altseason” has never been met.

Bitcoin Still Controls the Narrative

Despite growing interest in AI, meme, and DeFi tokens, Bitcoin still dominates crypto macro flows:

  • BTC ETFs continue attracting institutional capital

  • BTC.D (Bitcoin Dominance) remains elevated at 63%

  • Altcoin rallies remain fragile and dependent on BTC stability

That’s why, when Bitcoin dipped below $104K this weekend, altcoins didn’t decouple — they followed.

Final Thoughts — Far From Altseason

This month’s altcoin outperformance was real — but temporary. The Altcoin Season Index never confirmed the trend, and after Bitcoin’s minor drop, altcoin strength quickly faded.

Until BTC consolidates more cleanly, and the index breaks above 75, we’re still in a transition phase — not in altseason.

Traders should treat this as a rotational preview, not a full cycle shift. Selective plays may still work, but don’t expect the entire altcoin market to take off just yet.