The market's overwhelming 100% consensus on 14°C as London's highest temperature on May 15 stems from verified Met Office observations of persistent stratiform cloud cover, scattered light showers, and northerly breezes that suppressed solar insolation and advected a cool maritime air mass across southeast England. This setup followed an early-May Arctic outbreak that left residual below-normal temperatures, with afternoon peaks at London City Airport—the designated resolution station—held near 14°C amid high humidity and minimal diurnal warming. Model runs showed limited variance once midday conditions stabilized, aligning trader positions with official data rather than climatological averages around 17–18°C. A sudden afternoon clearance allowing stronger radiative heating or a southeasterly wind shift could have nudged readings to 15°C, but no such development materialized before resolution.