Recent model guidance and ensemble runs from the Met Office and ECMWF indicate overnight minima in London on August 21 will most likely settle in the 12–14 °C range, consistent with the market’s heavy weighting toward 13 °C and 14 °C. A shift to lower pressure and increased cloud cover is limiting daytime heating while allowing modest radiative cooling under lighter winds, pulling minimum temperatures a degree or two below the long-term August average of roughly 13–14 °C. Current short-range forecasts show a high near 19 °C and low near 14 °C, with some guidance dipping to 12 °C if clearer breaks develop overnight. Traders are responding to the narrow spread in deterministic and ensemble output, the proximity to resolution, and the absence of strong signals for either significantly warmer or colder air masses. Updated model cycles over the next 48 hours remain the key catalyst that could shift implied probabilities.