**Current forecasts from major models (GFS, ECMWF, and regional Brazilian guidance) place São Paulo’s overnight minimum on August 30 in the narrow 18–20 °C range, with the lowest readings most likely occurring just before dawn under partly cloudy skies and light easterly flow.** A warm, dry air mass currently dominates, suppressing strong radiative cooling and keeping dew points elevated, yet the absence of significant cloud cover or strong winds overnight allows modest cooling. Model consensus has tightened around 19 °C, but small differences in boundary-layer moisture, exact wind direction, and the timing of any weak frontal passage create the tight spread reflected in the 49 % / 44.5 % / 43 % market-implied probabilities for 18 °C, 17 °C or below, and 19 °C. Climatologically, late-August minima average near 12–14 °C, so the current elevated baseline keeps sub-17 °C outcomes possible only if clearer skies or a slightly stronger nocturnal inversion develop than most runs currently indicate. Traders are therefore weighting the latest high-resolution model runs and local CGE guidance, which will be updated within the next 24–36 hours as the event window approaches.