Recent forecasts from global models including GFS and ECMWF indicate Sao Paulo's overnight low on October 1 could range from the mid-teens to around 17°C, driven by variable cloud cover, scattered rainfall, and a possible weak frontal passage that modulates radiational cooling. Historical climatology places early October minimums near 16–17°C, with INMET outlooks favoring slightly above-average temperatures overall for the month, yet short-range runs diverge on the exact timing and intensity of any cooler air advection. This genuine uncertainty between sub-15°C outcomes and a milder 17°C floor explains the closely matched market-implied odds, as traders weigh the latest ensemble guidance ahead of final resolution.