Official observations from São Paulo-Guarulhos International Airport, the market's designated resolution source via Weather Underground, recorded a maximum temperature of precisely 30°C on April 17, 2026, driving the 100% implied probability on that outcome as traders await final data confirmation. Dry autumn conditions under a persistent high-pressure system suppressed cloud cover and humidity, enabling daytime heating to this level despite typical April highs averaging 25-26°C at urban stations; airport exposures often yield 2-4°C warmer readings in stable anticyclonic flow. Forecast models from INMET had projected 29-30°C peaks, aligning closely with observations. Realistic challenges would require post-finalization revisions to airport data—highly unlikely given standardized measurement protocols—or discrepancies across secondary stations, but current evidence overwhelmingly supports resolution to 30°C.