Trader consensus on Polymarket has locked in 13°C as the highest temperature in London on April 13 at 100% implied probability, reflecting the official Met Office observation from Heathrow Airport—the standard reference station for such markets—which recorded a maximum of 13°C amid unsettled weather patterns. This aligns with nationwide extremes showing 13.0°C as the UK's highest maximum that day at Altnaharra No. 2, driven by cyclonic systems bringing cooler air, cloud cover, and showers after an early-April hot spell exceeding 26°C in Kew Gardens. April climatology at Heathrow typically sees highs of 12–15°C, supporting this subdued outcome. Realistic challenges would require a rare data revision from measurement error or station-specific microclimate anomaly, though verification processes minimize such risks; the market nears resolution with no further updates expected.