Recent forecast models indicate an incoming frontal system will bring increased cloud cover and scattered showers to São Paulo on September 5, limiting solar heating and capping daytime maxima near 21–23 °C. A cold front that crossed the region in early September has already lowered baseline temperatures several degrees below seasonal norms, with surface high pressure and southeasterly flow maintaining stable, humid conditions that favor stratus development rather than strong insolation. Ensemble guidance from global models shows tight clustering around these values, with only modest spread tied to exact precipitation timing and boundary-layer mixing. Historical September climatology for the city centers near 23–25 °C, so the current pattern represents a modest negative anomaly driven by synoptic-scale cooling and reduced radiative forcing.