**Persistent cloud cover, thunderstorms, and high atmospheric moisture are the dominant factors keeping overnight lows in Guangzhou tightly clustered around 26–28°C on August 22.** Multiple forecast models show widespread rain and overcast skies expected through the night, which strongly suppress radiative cooling under clear conditions and elevate minimum temperatures relative to the long-term August average of ~25.4°C. Light winds and dew points near 26–28°C further limit nocturnal temperature drops by maintaining high boundary-layer humidity. Historical analogs with similar warm-sector rainfall patterns confirm that minima rarely fall below 25°C under these conditions, while drier breaks can allow brief dips toward 24°C. Slight model-to-model differences in precipitation timing and cloud thickness explain why the 26°C, 27°C, and 28°C outcomes trade so closely, with official China Meteorological Administration observations serving as the resolution source.