Persistent rain, thunderstorms, and extensive cloud cover over Taipei are the dominant factors capping daytime heating and aligning trader sentiment with 29–31°C outcomes for September 4. Official Central Weather Administration guidance and multiple forecast models project a high near 29–30°C under continued moist easterly to northerly flow, with limited solar insolation and high humidity suppressing maxima below seasonal averages near 31–32°C. Light variable winds further reduce mixing and peak temperatures. Recent model runs show only modest day-to-day shifts, leaving the narrow spread between 30°C and 31°C largely driven by uncertainty in exact rainfall timing and intensity. The market will resolve on the official daily maximum recorded at the primary Taipei station.