Recent Copernicus ERA5 data confirm September 2026 as the second-warmest September globally after 2023, with an anomaly of 1.63°C above pre-industrial levels, aligning with the market's 97% implied probability for second place. Persistent El Niño conditions in the equatorial Pacific boosted sea surface temperatures and atmospheric heat content through the Northern Hemisphere summer, sustaining the long-term warming trend driven by greenhouse gas accumulation. August 2026 tied the all-time monthly record, providing a warm baseline that carried into September. Final rankings could shift only if major revisions emerge from other agencies like NOAA or if an unexpected cooling bias appears in observational datasets, though current model consensus and early October analyses make such reversals highly unlikely.