The dominant 100% market-implied probability for a 20°C high in São Paulo on September 5 reflects confirmed observational data from Brazil’s national meteorological service showing that temperature as the daily maximum. Official station readings, taken under World Meteorological Organization standards, captured peak values at or near 20°C amid stable subtropical high-pressure conditions and minimal diurnal warming. Historical September climatology for the region, with typical highs around 22–26°C, placed this outcome slightly below average yet fully consistent with the verified record. Near-certainty leaves little room for alternative outcomes, though final dataset revisions or quality-control adjustments by the reporting agency could theoretically alter the precise maximum before market resolution.