The strengthening El Niño, with Niño-3.4 anomalies reaching +1.8°C and models favoring a historic-strength event through late 2026, combined with record ocean heat content, forms the main driver behind the 64.5% trader consensus on a 1.35–1.39°C September global mean surface temperature anomaly relative to pre-industrial levels. NOAA and Copernicus data show August 2026 already at 1.32–1.65°C above baselines amid the warmest meteorological summer on record, while background greenhouse-gas forcing sustains the long-term trend. ENSO outlooks from CPC and IRI indicate further warming into fall, though model spread and potential rapid shifts in equatorial Pacific conditions introduce uncertainty around exact monthly resolution.