**Stable high-pressure conditions and clear skies are supporting overnight radiative cooling toward minimum temperatures near 18–22°C for Beijing on September 4, 2026.** Multiple forecast models and official guidance from sources including the China Meteorological Administration show a daytime high of 32–33°C under mostly sunny skies with light variable winds (generally under 3 m/s), followed by clear to partly cloudy nighttime conditions. This setup favors efficient longwave radiative heat loss after sunset, with dew points in the mid-teens °C limiting further cooling once saturation approaches. The tight clustering of market-implied probabilities around 18–19°C (50.5%) versus nearby bins reflects modest ensemble spread in overnight minimums. Key differentiating factors include exact wind speeds (calm conditions enhance cooling), boundary-layer humidity, and the strength of the urban heat island effect in central Beijing, which can add 1–2°C relative to rural sites. Historical early-September climatology for Beijing features average lows near 15–18°C, but the current warm, dry air mass has kept recent nights milder. No significant synoptic changes (such as approaching fronts) are expected before September 4, keeping the forecast stable. Later cooling on September 7–8 from increased clouds and rain will not affect this resolution window. Updated model runs or official minimum observations from Beijing stations on the morning of September 5 will provide the decisive data for market resolution.