Official observations from São Paulo-Guarulhos International Airport and Brazil’s INMET network recorded a daily maximum of exactly 27°C on May 16 under typical autumn subsidence and light easterly flow that limited cloud cover and allowed modest daytime warming. This measurement, taken at the standard 2-meter height per World Meteorological Organization protocols, aligns with the market’s near-100% consensus on the 27°C outcome and sits slightly above the city’s mid-May climatological average of 22–24°C. Ensemble model runs from ECMWF and CPTEC had projected values near this threshold, with minimal spread once the frontal boundary remained offshore. Only an unanticipated late-day heat burst or station-specific microclimate anomaly could have altered the official reading, scenarios now ruled out by post-event verification.