**Incoming cold air and widespread rain are creating forecast uncertainty around Chengdu’s overnight low on September 9.** Official Chinese meteorological guidance and multiple models indicate a sharp cooling episode from September 8–10, with daytime highs dropping 5–7 °C to the mid-20s °C and northerly winds strengthening to 4–7 on the Beaufort scale. Heavy to moderate rain (locally torrential in western districts) is expected through the night of the 8th into the 9th, which suppresses daytime heating and enhances evaporative and cloud-cover cooling at night. Model consensus points to a minimum near 17–20 °C, but small differences in the timing of the frontal passage, rainfall intensity, and boundary-layer mixing produce a wide plausible range. Some runs allow the low to dip to 16 °C or below under clearer breaks or stronger advection, while others keep readings closer to 20–22 °C if clouds and rain persist longer. Historical September climatology for Chengdu shows typical overnight lows in the upper teens to low 20s °C, so this event sits near the cooler tail but remains within seasonal variability. Traders are therefore split between the ≤16 °C bucket and the ≥26 °C bucket (both near 49–50 % implied probability), with individual integers around 21–25 °C each trading near 24–25 %. The wide dispersion reflects genuine short-term forecast spread rather than any long-term trend; the next 24–48 hours of updated model runs and local observations will be the decisive inputs before resolution.