Trader consensus has locked onto a 21°C high for Seoul/Incheon on October 1 because official forecasts and real-time observations from the Korea Meteorological Administration and Incheon International Airport station converged on this exact maximum under clear to mostly clear skies, light northwest winds, and dry autumn conditions. Multiple model runs and hourly data showed afternoon peaks reaching but not exceeding 21–22°C, consistent with climatological norms for early October in the region. This skin-in-the-game outcome reflects the low uncertainty in short-range temperature forecasting once diurnal heating peaks. A realistic challenge would require an official measurement revision or station-specific reading above the threshold, though current data make such shifts unlikely.