Recent forecasts from multiple models show Sao Paulo overnight lows near 17–18°C on October 5 amid persistent cloud cover, high humidity, and scattered rain, consistent with the spring transition to the wet season that limits radiative cooling. Elevated moisture and overcast skies suppress temperature drops compared to clearer conditions, while steering patterns and frontal activity introduce variability in exact minima. Market-implied odds near 50% for both sub-14°C and 24°C+ extremes reflect model spread and sensitivity to small shifts in precipitation timing or cloud thickness, with specific 18–23°C outcomes clustered around 34% capturing the consensus range. Updated model runs and official monitoring will clarify resolution thresholds ahead of the date.