**Incoming cold air and a shear line are driving modest overnight cooling in Chongqing for October 13, with official forecasts showing a minimum near 20–21 °C amid persistent cloud cover and light rain.** Multiple model runs and agency outlooks indicate highs around 26–27 °C and overnight lows of 19–21 °C, consistent with the market’s leading 20 °C outcome at 41 % implied probability. Key variables separating the clustered 17–19 °C probabilities include the precise timing and depth of cold-air advection, the extent of low-level cloud that limits radiative cooling, and local humidity effects on dew-point depression. Historical October minima average near 16 °C, but the current pattern remains warmer than climatology due to lingering warmth ahead of stronger cooling expected later in the week. Updated model guidance and observational data from the China Meteorological Administration will refine these thresholds ahead of market resolution.