Official Met Office observations confirm the highest temperature in London on May 13 reached exactly 13°C, anchoring trader consensus at a 100% market-implied probability for this outcome as aggregated sentiment backed by real capital. This positioning stems from precise, synchronized air temperature measurements—taken via standardized, calibrated thermometers at 1.25–2 meters above ground—at key sites including Heathrow Airport and St James's Park, adhering to World Meteorological Organization protocols. Amid below-average conditions for mid-May (historical highs around 16–18°C), no station exceeded this mark during the 24-hour period. Realistic challenges are minimal but could involve post hoc quality control revisions uncovering sensor discrepancies or debates over the defining London reference site, though such shifts are rare after initial daily summaries.