Trader sentiment for São Paulo’s August 22 minimum temperature remains closely balanced because ensemble forecasts diverge on the extent of nocturnal radiative cooling. Models show a dry, stable airmass with light winds favoring clear skies and strong surface heat loss, which could push readings at official stations like Mirante de Santana into single digits or lower. Countervailing factors include modest warm advection aloft and the urban heat-island effect that often keeps city-center lows 2–4 °C above rural sites. The slight edge for 4 °C or below (35.5 %) reflects the tail risk of an unusually clear, calm night, while probabilities clustered near 11–12 °C capture the more likely outcome if even thin cloud or light mixing develops. Updated model runs and satellite imagery tonight will clarify whether the coldest scenario materializes.