Recent forecasts from the Met Office and BBC Weather indicate London will see sunny intervals on August 15 with a daytime maximum near 27°C, but overnight radiative cooling under largely clear skies points to a minimum around 15–16°C. Trader consensus favoring 20–21°C as the lowest temperature likely reflects the urban heat island effect in central London, where concrete and reduced sky view factors limit nighttime cooling compared to suburban or rural sites, combined with light winds that reduce mixing. Persistent high pressure and recent heatwave conditions have kept baseline temperatures elevated, narrowing the spread between 20°C and 21°C outcomes while leaving room for slight downward revisions if stronger northerly flow arrives earlier than models suggest. Updated ensemble runs and official observations on the day will be decisive for resolution.