Traders see closely matched odds between a minimum of 30°C or higher and 20°C or below in Chongqing on September 28 because short-range forecast models diverge on overnight cooling. The city’s Sichuan Basin location promotes temperature inversions and persistent humidity that typically limit diurnal drops, yet late-September frontal passages or variable cloud cover can enhance radiative cooling and push lows lower. Global ensembles and China Meteorological Administration guidance currently show a wide spread in predicted minimums tied to uncertain wind patterns and precipitation timing. New model runs and observational updates overnight will likely narrow the range ahead of market resolution.