Forecast models for São Paulo on August 25 project a daily maximum near 21–22 °C under persistent stratiform cloud cover driven by moist southeasterly flow off the Atlantic. This maritime advection suppresses diurnal heating by limiting surface insolation while maintaining high relative humidity and modest wind speeds that inhibit boundary-layer mixing. Recent observations show the same pattern holding through late August, with highs running 1–3 °C below seasonal normals amid stable high pressure and no strong frontal passages. Traders assign the highest probabilities to 21 °C and 22 °C because ensemble guidance clusters tightly around these values, with only modest spread arising from small differences in cloud optical depth and exact timing of any partial clearing during the afternoon heating window.