Recent KMA and international model guidance for August 20 point to partly to mostly cloudy skies with a 20–30% chance of showers, keeping peak temperatures near or slightly below seasonal norms for mid-August in the Seoul-Incheon region. The close clustering of market-implied odds around 28–30°C reflects uncertainty in afternoon cloud cover and convective timing, which can suppress maximum solar insolation and limit surface heating by 2–4°C compared with clearer scenarios. Steep humidity and a weak pressure gradient further moderate the urban heat island effect, while any earlier clearing or delayed precipitation would favor the 31°C tail. Updated short-range runs from the Korea Meteorological Administration and ensemble guidance expected in the next 24 hours will likely sharpen resolution between these narrow thresholds.