Rapidly increasing chance of record UK summer temperatures

The UK recorded its first exceedance of 40°C in July 2022. To assess the current chance of recurrence, we use a large climate model ensemble approach and find the 2023 return period to be 1‐in‐24 years (1/20–1/29 years confidence interval). However, the likelihood of 40°C has been accelerating and we estimate a 50–50 chance of another exceedance in the next 12 years, 4 years earlier than in a static 2023 climate. Far higher temperatures – over 45°C – and more sustained heatwaves may be possible today. Improved understanding of baseline exposure to temperature extremes could inform strategic heatwave preparation.