Latest China Meteorological Administration and global model ensembles project Beijing’s May 17 high near 20–21 °C amid a weak cold front delivering northerly winds, scattered light rain, and persistent low cloud cover that sharply curtails daytime solar heating. This setup creates the tight clustering of market-implied odds around 19–21 °C, with differentiation driven by exact frontal timing and boundary-layer mixing: earlier clearing or stronger insolation would favor 22 °C or higher, while prolonged overcast and wind shear keep readings capped at 19 °C or below. Historical May climatology shows similar frontal passages typically suppress peaks by 3–5 °C relative to clear-sky baselines, and updated ECMWF and GFS runs expected this evening will refine the precise temperature trajectory before resolution.