Recent model runs from major forecasting centers indicate a persistent warm air mass over southern England, with limited nocturnal cooling under partly cloudy skies and light winds, pushing the market-implied odds toward 19–20°C as the most probable overnight low for London on August 13. This reflects ensemble guidance showing minimum temperatures several degrees above the August climatological average of roughly 14–16°C. Differentiation between the leading outcomes hinges on subtle forecast uncertainties in cloud cover timing and boundary-layer mixing, which can alter radiational cooling rates by 1–2°C. Traders are weighting the latest high-resolution runs and statistical post-processing, with resolution hinging on official Met Office observations at standard sites; any late adjustments in the 48-hour window could shift probabilities between these closely matched bins.