**Forecast models converge on a 24–26°C range for Shanghai’s September 29 high, supporting the tight market split between 25°C (42%) and 26°C (38%).** Persistent cloud cover, moderate-to-heavy rain, and easterly/northeasterly flow associated with a passing weather system limit daytime solar heating and promote evaporative cooling. Official guidance from multiple sources shows highs near 25–26°C (78–79°F) under overcast, rainy conditions, consistent with late-September subtropical monsoon patterns where moisture and reduced insolation typically cap peaks below seasonal averages. Model consensus remains stable within the past 24–48 hours, with only minor spread in exact maxima depending on rainfall timing and intensity. Resolution will hinge on the official daily maximum recorded by local meteorological stations, sensitive to brief clearing or heavier showers.