**Recent KMA forecasts for Seoul/Incheon on August 21 point to a daytime maximum near 29°C under mostly cloudy skies with afternoon rain (60% probability), following overnight lows around 25°C.** This aligns with the market's top outcomes clustered at 27–29°C (combined ~80% implied probability), reflecting traders' assessment of moderating late-summer conditions after the early-August heatwave that produced national records above 40°C. Key scientific drivers include the seasonal decline in solar insolation and strengthening monsoon influences, which increase cloud cover, humidity, and convective precipitation that limits afternoon heating. Steering patterns and model consensus favor a relatively stable air mass without strong subsidence or clear-sky radiative warming that could push readings into the low 30s. Historical analogs for late August show average highs falling from ~29–30°C early in the month toward 27–28°C by the third week, consistent with current observational trends and ensemble guidance. Upcoming KMA updates and any shifts in precipitation timing or intensity remain the primary variables that could nudge the highest temperature across the 27–29°C threshold before resolution.