Official Met Office observations from key London stations, including Heathrow, confirm the lowest temperature on May 4, 2026, was exactly 12°C, driving unanimous trader consensus at 100% implied probability. Persistent low cloud and overcast conditions during the early May bank holiday weekend suppressed radiative cooling overnight—typical in such setups where insulation from cloud layers keeps surface air warmer than clearer skies would allow—resulting in minima above pre-event model forecasts of 6–8°C from sources like the UKV model. This aligns with climatological norms for early May in London, where average overnight lows hover around 8–10°C. Scenarios challenging this include rare data revisions from quality control or overlooked rural station readings, but standardized verification processes make shifts improbable as final datasets solidify.