Official Met Office observations from key London stations, including Heathrow, confirm the highest temperature on May 3, 2026, peaked at 20°C amid sunny intervals transitioning to increasing cloud cover and light southerly winds around 8-10 km/h, which limited further solar heating after midday. This verified measurement, aligning closely with pre-event forecast model consensus from the UKV and global ECMWF ensembles projecting 19-21°C maxima, underpins the market's 100% implied probability on 20°C as traders aggregate real-time synoptic data with skin-in-the-game precision. While early May climatology typically sees London highs near 17°C, yesterday's conditions fit mild high-pressure influence without anomalous warmth. Realistic challenges include minor data quality revisions in final validation or a late-submitted outlier from peripheral sites like Kew Gardens exceeding 20°C, though unlikely given standardized reporting protocols; watch for Met Office's monthly summary for closure.