**Forecast uncertainty around overnight radiative cooling and precipitation is driving closely matched trader probabilities across 17–22°C outcomes for Beijing’s minimum temperature on August 27.** Numerical weather models show a transition to cloudier, more humid conditions with light rain or drizzle possible, which limits daytime heating while potentially enhancing overnight cooling through increased moisture and variable wind patterns. Recent runs indicate lows in the 17–21°C range, consistent with late-August climatology (average minimum near 20°C) but with notable ensemble spread due to steering flow and timing of any frontal passage. This genuine model disagreement—typical when resolution thresholds fall near the diurnal minimum—explains why no single outcome exceeds ~32% implied probability. Traders are weighting official updates from the China Meteorological Administration and fresh high-resolution model guidance expected before dawn on the 27th, as those will determine whether the night stays near 21–22°C or dips toward or below 17°C.