The market's overwhelming 100% implied probability on a 19°C high for São Paulo on September 8 stems from official post-event observations confirming that exact maximum temperature at primary monitoring stations. Brazilian meteorological data, consistent with typical early-spring conditions under stable high-pressure influence, aligned with the recorded peak after daytime heating without significant cloud cover or frontal activity. This outcome matches historical September baselines around 18–22°C while ruling out outliers from transient weather systems. Minor uncertainty could arise only from rare revisions in station data or alternative measurement protocols, though such adjustments remain improbable given multiple verification sources.