**Short-term forecast uncertainty from variable spring weather patterns is keeping market-implied odds nearly even between cooler and warmer outcomes for São Paulo’s minimum temperature on October 2.** Official and ensemble models currently indicate overnight lows near 12–17°C, influenced by a mix of cloud cover, light rain, and residual moisture that can either enhance radiative cooling or moderate temperature drops. In the Southern Hemisphere spring, shifting steering patterns and frontal boundaries introduce notable spread in guidance, with some runs favoring clearer skies and stronger cooling toward the 11°C threshold or below, while others project warmer advection pushing minima to 21°C or higher. Historical October lows average 15–18°C, but daily variability from precipitation and humidity adds resolution risk around specific bins like 16–18°C. Traders will monitor updated NWP runs and regional observations in the final 48 hours for clearer signals on nocturnal boundary-layer conditions.