Recent medium-range forecasts show notable spread in London's overnight minimum for August 5, with Met Office guidance pointing toward 15°C while other ensembles and guidance suggest 17–19°C amid continued above-normal warmth. Primary drivers include variable cloud cover modulating radiative cooling, light winds limiting turbulent mixing, and the urban heat island effect at the London City Airport station, which typically elevates readings several degrees above rural baselines. High-pressure dominance favors clearer skies and milder advection of subtropical air, yet subtle differences in model handling of boundary-layer moisture and frontal approaches create the tight clustering around 15–19°C outcomes. Updated runs from ECMWF and UKV models over the next 48 hours will likely narrow this uncertainty before resolution.