**Sustained exceptional warmth across meteorological summer (June–August) 2026 has driven the 89% market-implied probability that it will set a new UK mean-temperature record.** Provisional Met Office data show the June 1–August 10 mean already at 16.48°C—1.88°C above the 1991–2020 average and well ahead of the 16.10–16.12°C mark set by the previous record holder in 2025. Only near- or slightly-below-average conditions are now required for the remainder of August to confirm the outcome. Multiple heatwaves, including a late-June episode that produced provisional national June maxima of 37.7°C (England) and 35.9°C (Wales), plus an August peak of 38.1°C, have contributed. The season has also featured the earliest and most frequent days above 35°C on record, elevated overnight minima (“tropical nights”), and prolonged high-pressure patterns that suppressed cloud cover and rainfall. These conditions align with the long-term trend of increasing temperature extremes linked to human-induced climate change. As of late August, the final days of meteorological summer remain, but the accumulated anomaly and limited remaining window make a new record the strong consensus outcome among traders. Updated Met Office verification and final seasonal statistics will provide definitive resolution.