Trader consensus on Polymarket pins the highest temperature in Shanghai on March 19 at exactly 12°C, propelled by converging forecasts from authoritative models like ECMWF and GFS, projecting daytime highs of 11-13°C under cool northerly winds, overcast skies, and a stable upper-level trough. Historical March climatology supports this, with Shanghai's average highs around 12°C and recent observations from Pudong stations confirming chilly conditions. Ensemble spreads remain tight, implying high confidence. Challenges could arise from an unexpected warm front or model underestimation of insolation—common spring variabilities that occasionally boost temps by 1-2°C—but current synoptic patterns make 13°C or higher unlikely.