Official measurements from Brazil’s Instituto Nacional de Meteorologia (Inmet) at the Mirante de Santana station confirmed a daily maximum of 16°C in São Paulo on September 14, 2026, locking in the market’s near-certain outcome. Persistent heavy rainfall—already pushing the month toward record totals more than three times the climatological average—combined with extensive cloud cover and advection of cooler maritime air kept temperatures well below seasonal norms. Model guidance and surface observations showed limited diurnal warming under overcast skies, with highs consistently reported in the mid-teens Celsius. While minor station differences or rounding conventions could theoretically affect resolution, the consensus across official networks leaves little realistic room for deviation from 16°C.