Recent heavy rainfall forecasts and influx of cooler northern air are the dominant drivers behind the tight clustering of Polymarket odds around 21–24°C for Chongqing’s August 29 minimum. Official guidance from the Chongqing Meteorological Bureau highlights a strong precipitation event from late August 28 into August 29, with mid-western districts expecting 30–80 mm (locally >100 mm) of rain, 6–9 grade gusts, and daytime maxima falling to 27–31°C. Cloud cover, evaporative cooling, and advection of lower dew points suppress nocturnal temperatures below recent August baselines near 26–28°C. Ensemble model consensus supports a minimum near 22–24°C, with minor spread arising from uncertainty in exact rain timing and boundary-layer moisture; traders therefore price nearby bins nearly equally while discounting extremes above 25°C or below 20°C.