**Persistent high-pressure dominance and coastal moderation shape the tight 33–35°C cluster for Incheon’s August 9 maximum.** South Korea remains under an intense heatwave, with KMA observations showing recent Incheon highs of 34°C on August 5 and 35°C on August 6 amid record national readings elsewhere. Medium-range guidance and ensemble spreads indicate continued subsidence and clear skies through the weekend, supporting afternoon peaks near or slightly above climatological August values (typically 29–31°C at the airport station), yet light easterly flow and marine influence limit further intensification. Model consensus highlights modest day-to-day variability from possible weak sea-breeze effects or isolated afternoon convection on August 8–9, which could trim the peak by 1–2°C or allow it to reach the upper end of the envelope depending on timing and coverage. This genuine forecast spread—rather than any single outlier run—explains why traders assign the highest implied probabilities to the central 33–35°C outcomes while assigning low single-digit odds to 36°C or higher. Updated KMA short-range guidance and next model cycles will refine these odds ahead of resolution.