**Trader consensus has converged on 26°C as the highest temperature in Chengdu on September 17, 2026, reflecting near-certainty from aggregated forecasts and early observations.** Multiple meteorological sources, including local reports and model outputs, indicate a daytime peak around 25–26°C under partly cloudy to overcast conditions with light rain or drizzle possible, consistent with typical late-summer patterns in the Sichuan Basin where high humidity and weak winds limit stronger warming. This aligns with historical September averages near 25°C and recent days showing similar maxima amid stable atmospheric conditions. The market-implied probability exceeds 99% because official station readings or the resolution source are expected to confirm this threshold without significant deviation. A realistic challenge would require an unexpected late-day surge from clearer skies or model error pushing the official high to 27°C or higher, though current data and timing make this highly unlikely before resolution.