Recent forecast models for São Paulo on October 16 indicate overnight lows near 17–19°C amid widespread showers and thunderstorms driven by a frontal system and above-average spring rainfall. Persistent cloud cover and evaporative cooling from precipitation support the market’s elevated weighting on outcomes at or below 15°C, while historical mid-October averages around 16–17°C and current ensemble guidance temper probabilities for warmer thresholds. Steep humidity levels near 90% overnight and moderate northwest winds further limit radiative cooling, creating a narrow range where small shifts in storm timing or intensity could push the daily minimum across key resolution boundaries. Updated runs from agencies like INMET or global models will likely refine these implied probabilities ahead of the overnight period.