**Market-implied odds show 24–25°C as the clear frontrunners (combined ~73% probability), reflecting tight scientific uncertainty in overnight minimum temperatures for Seoul/Incheon on August 18.** Mid-August climatology in the region features persistently high humidity (often 70–85%) and frequent cloud cover that restricts radiative cooling after sunset, keeping overnight lows near or slightly below the seasonal average of ~23–24°C. Recent KMA short-range guidance and observations indicate mostly cloudy to partly cloudy conditions through August 17 with showers, which trap heat near the surface and support minimums around 24–25°C. A forecast shift toward mostly sunny skies on the 18th could allow marginally greater nocturnal cooling, but urban heat-island effects and light winds in the Seoul-Incheon corridor limit how far temperatures can drop. The narrow 1°C spread between the top two outcomes stems from small differences in ensemble model runs for boundary-layer moisture, cloud timing, and wind speed—variables that directly influence the rate of heat loss after midnight. No major synoptic features such as typhoons or cold fronts are currently indicated, so probabilities remain anchored to these routine summer conditions and the latest official forecast updates expected in the next 24–48 hours.