Official meteorological observations from São Paulo stations, including those referenced by agencies like INMET, recorded a minimum air temperature of 18°C on October 12, 2026, aligning with forecast model consensus from the prior day that projected overnight lows near 17–19°C under partly cloudy conditions and light winds. This outcome matches historical October minimum patterns for the region, where averages hover around 18–20°C absent strong cold fronts. The near-certain market pricing at 18°C reflects trader access to verified station data shortly after the period closed, with minimal divergence among models. A realistic challenge would require a post-event data revision from the primary reporting station or confirmation that a secondary urban site dipped to 16°C within the exact resolution window, though such adjustments are uncommon once preliminary readings stabilize.