Recent Met Office regional guidance and ensemble model runs indicate a warm but not extreme pattern for London on August 4, with southerly flow and high pressure supporting daytime maxima near 28–29°C under mostly sunny conditions before increasing humidity and shower risk. This aligns with the market’s leading implied probabilities for those thresholds, reflecting 2026’s broader above-average summer temperatures and multiple prior heat periods that have elevated baseline warmth by roughly 2–3°C across southern England. Official measurements at London-area sites incorporate the urban heat island effect, while forecast uncertainty centers on exact cloud cover and any Atlantic frontal timing that could cap peaks below 28°C. Traders are monitoring the next Met Office and ECMWF updates for refinements ahead of the Tuesday resolution window.