**Provisional Met Office data released in early September 2026 shows summer (June–August) mean temperatures reached 16.5°C across the UK, exceeding the prior 2025 record of 16.1°C by a wide margin and ranking as the warmest since records began in 1884.** Multiple heatwaves, including nine days above 35°C and new June and August maxima near 38°C, combined with elevated overnight minima to drive the seasonal average 1.9°C above the 1991–2020 baseline. Attribution analysis indicates human-induced climate change made such warmth roughly 130 times more likely. With final verification still pending, the scale of the anomaly makes any reversal improbable, underpinning the 98.4% market-implied probability for a new record.