Trader consensus on Polymarket heavily favors 11°C (30.5%) and 12°C (28.5%) as London's highest temperature on March 29, reflecting the latest Met Office and ECMWF model ensembles that project maximums in this narrow range amid persistent low cloud cover and a mild southerly airflow. These closely matched implied probabilities underscore inherent forecast uncertainty at the integer-degree level, driven by variable solar insolation under overcast skies—thicker cloud decks could cap peaks at 11°C, while brief breaks might allow 12°C, as seen in recent 24-hour model runs showing minimal shifts. Climatologically, late March highs average 11-12°C at Heathrow (the official measurement site), with low wind shear limiting convective heating; traders await final hourly guidance updates before resolution.