Ethereum finished September 2026 at +8.8%. If you held only the best days, the return jumps to +31.4%, while missing them drops it to -17.2%. That tells you the month was driven by a handful of outsized sessions rather than smooth trend strength. The biggest upside day was 9/18/26 (+7.2%), and the roughest day was 9/15/26 (-5.4%) $ETH