Numerical weather prediction models from the Korea Meteorological Administration indicate a daytime high near 28–30°C for Seoul on May 18 under clear to partly cloudy skies and light westerly flow, positioning the 25°C-or-higher outcome as the clear market leader at 62% implied probability. This aligns with late-spring warming driven by a strengthening subtropical ridge that has elevated temperatures several degrees above the mid-May climatological average of 23°C. Recent short-range runs show minimal model spread, with only modest uncertainty from possible afternoon cloud development or slight timing shifts in peak insolation. Traders are monitoring the next model update cycle on May 17 for any revisions to wind speed or humidity that could trim the high by 1–2°C.