Current atmospheric patterns over East Asia, with a building high-pressure ridge and light southerly flow from the Yellow Sea, favor daytime maxima in Seoul near 24–26°C on May 19. Ensemble guidance from the Korea Meteorological Administration shows partly cloudy skies and minimal frontal passage, allowing moderate solar heating while limiting moisture-driven suppression. These variables explain the tight clustering of market-implied odds around 25°C, where a modest increase in cloud cover or wind shift could drop the peak by 1–2°C or permit a brief spike higher. Mid-May climatology places the seasonal average high near 23°C, underscoring why traders assign low probability to values outside this narrow band.