**Forecast consensus for Chengdu’s overnight low on August 30 centers on 22–24 °C, with Polymarket odds tightly clustered (23 °C at 48 %, 22 °C and 24 °C near 47 %).** This reflects the narrow but genuine uncertainty in numerical weather prediction outputs for nocturnal radiative cooling under late-summer subtropical monsoon conditions. Chengdu lies in the Sichuan Basin, where light winds (often <2 m s⁻¹), high boundary-layer humidity (50–80 %), and variable cloud cover limit the rate of surface heat loss after sunset. Recent model guidance shows daytime highs near 31–33 °C on the 30th followed by partly cloudy skies and dew points around 20–22 °C, supporting minimums in the low-to-mid 20s °C. Small differences in predicted cloud thickness or wind speed—factors that alter downward longwave radiation and turbulent mixing—shift the expected low by 1–2 °C across ensembles, explaining the near-equal probabilities for 22–24 °C. Lower outcomes (20–21 °C) would require clearer skies and slightly drier air allowing stronger radiative cooling, while values above 24 °C would need greater cloud cover or residual moisture from any showers on the 29th. Historical August minima average near 22 °C, and current conditions lack strong synoptic forcing (e.g., persistent high pressure or monsoon surges) that would push extremes. Traders are therefore pricing the high-resolution forecast spread rather than any single deterministic run.