Recent forecasts from multiple models point to a cold front crossing São Paulo on September 1, driving cooler, moist northwesterly then southerly flow with widespread rain and cloud cover that limits daytime heating while enhancing overnight radiative cooling. This setup creates tight clustering around 14–16 °C minima, as the precise arrival timing of the front, rainfall duration, and boundary-layer wind shifts determine whether the city’s urban heat island keeps readings near 16 °C or allows a deeper drop to 14 °C or below. Historical September climatology shows average lows near 12–15 °C, so the current pattern aligns with seasonal norms yet carries model spread typical of frontal passages. Updated INMET and global model runs in the next 24–48 hours will sharpen the distinction among these closely matched outcomes.