Recent KMA forecasts and ensemble models highlight afternoon showers with 60% precipitation probability and variable cloud cover as the dominant driver behind the tight clustering of market-implied odds around 27–29°C for Busan’s August 17 maximum. Persistent southerly flow along the North Pacific High favors typical August coastal highs near 29–31°C, yet timing and intensity of rain introduce key uncertainty: earlier or heavier showers suppress peak temperatures through reduced insolation and evaporative cooling, favoring 27°C outcomes, while delayed or lighter activity allows brief warming toward 29°C. Sea breezes and high humidity further moderate extremes, with traders weighing model consensus against historical August variability for resolution.