Recent Met Office and ensemble model guidance point to a daytime maximum of 24–26 °C in London on 27 August, with the market’s tight clustering around 25 °C reflecting uncertainty over afternoon cloud breaks and shower timing. A warm, humid airmass advected from the south is being modified by an approaching Atlantic front that brings overnight and morning rain, followed by gradual clearing that permits limited insolation. Southwesterly winds of 3–5 m/s will enhance mixing and cap peak heating, while variable cloud cover and localized convection introduce a roughly 2 °C spread across guidance. Official resolution will hinge on the highest 1-minute or hourly reading recorded at an approved London station before midnight.