Trader consensus at 100% implied probability on a 24°C high for Seoul/Incheon on September 15 reflects official station readings from the Korea Meteorological Administration and Incheon International Airport, where afternoon maxima stabilized at that level under clear skies, light northwesterly winds around 6–8 kt, and low humidity near 30–50%. These conditions aligned with model consensus from GFS runs showing limited diurnal heating and no significant warm advection, consistent with typical mid-September climatology for the region. The near-certainty accounts for the day nearing completion in local time, with minimal scope for revision. Only an improbable late surge from unforecast mesoscale features or measurement error at primary sites could alter the outcome before final verification.