Official forecasts for São Paulo on August 23 project overnight lows near 9–13°C under mostly clear to partly cloudy skies with light winds, aligning closely with typical Southern Hemisphere winter climatology (historical August minima averaging 12–14°C at urban stations). This narrow band of model consensus—driven by stable high-pressure dominance and absence of strong cold fronts or polar air incursions—explains the tightly clustered market-implied probabilities across 8–13°C outcomes. Resolution hinges on the official minimum recorded at the primary INMET reference station, where urban heat effects and exact timing of the diurnal minimum introduce residual uncertainty even as traders weigh recent model runs showing minimal day-to-day variance.