Forecast uncertainty for Guangzhou's minimum temperature on September 1 stems from diverging global model guidance on the arrival and strength of a mid-latitude frontal boundary interacting with subtropical moisture. Ensemble runs show variable timing of cooler northerly flow versus persistent warm, humid southerly air, producing a bimodal distribution where daily lows could dip to 20 °C or below under stronger cold advection or remain near or above 30 °C if the front stalls. Historical September climatology places average minimums near 24–26 °C, so resolution hinges on the next 48-hour model updates from agencies such as the China Meteorological Administration and ECMWF, which traders monitor for shifts in 850 hPa temperatures and precipitation timing.