Trader consensus assigns a 90% implied probability to 13°C as Sao Paulo’s lowest temperature on September 16, reflecting post-event meteorological observations and model agreement. Clear skies overnight enabled strong radiational cooling under a stable high-pressure ridge, while regional wind patterns limited mixing of warmer air. September climatology for the city typically features nighttime lows of 12–14°C, providing a baseline that aligns with the leading outcome. Official confirmation from Brazil’s National Meteorological Institute is anticipated shortly, with any revisions to the recorded minimum likely to shift remaining probabilities among the lower-temperature options.