Recent forecast consensus points to a sharp cooldown in São Paulo on September 1 driven by a cold front arriving from the south, with northwest winds, extensive cloud cover, and widespread thunderstorms expected to limit daytime heating. Official model guidance from sources including the Met Office and local meteorological services centers daily highs near 20–24°C, aligning with the market’s tight clustering around 22–24°C. This follows unusually warm late-August conditions exceeding 32°C. Persistent rain, elevated humidity near 85–90%, and reduced solar insolation under overcast skies are the dominant variables that could shift the precise maximum by 1–2°C depending on the timing of heaviest precipitation. Historical September averages near 23–25°C provide context, but the active frontal dynamics introduce short-term uncertainty ahead of final resolution.