**Trader sentiment for Beijing’s September 26 minimum temperature reflects tight model spread around 17–18 °C, with the 47 % probability on 13 °C or below and 44.5 % on exactly 18 °C capturing residual forecast uncertainty.** Official guidance from the China Meteorological Administration and ensemble runs show overnight lows near 17–18 °C under partly cloudy skies and light northerly flow following daytime showers. Radiative cooling will be moderated by lingering moisture and variable cloud cover, while any earlier or more widespread rain could suppress the minimum by 1–2 °C through evaporative effects. Historical late-September climatology places typical overnight lows near 16–18 °C, so current guidance aligns closely with the median. Fresh model updates and surface observations through the night will be the key catalysts likely to shift the tightly bunched probabilities before resolution.