**Forecast models from the UK Met Office and other sources indicate a daytime maximum of around 21°C for London on August 29, 2026, under unsettled conditions with rain and thick cloud cover.** This aligns closely with the market-implied probabilities, where 21°C leads at 45.5% and 20°C follows at 35.5%, reflecting trader consensus on modest temperatures amid Atlantic-influenced weather. Late August climatology for London shows average highs near 22–23°C, but a southwesterly flow and incoming frontal system are suppressing warming through reduced insolation and evaporative cooling from precipitation. Hourly data point to peaks in the low 20s Celsius during the afternoon before rain intensifies, with overnight lows around 17°C. Model consensus emphasizes limited diurnal range due to persistent cloud and moderate winds (gusts to 26 mph), keeping values well below any heatwave thresholds. Recent developments include the arrival of a low-pressure system overnight, shifting conditions from clearer spells on the 28th to widespread rain and possible thunderstorms on the 29th. This pattern matches historical analogs for cool, wet late-summer days and explains why higher outcomes (22°C+) hold only single-digit implied odds. Updated official guidance and real-time observations from stations like Heathrow will drive any final adjustments before resolution.