The closely bunched probabilities for 13–16°C capture the modest spread in short-range ensemble forecasts for Seoul’s overnight minimum on May 18. Recent global model runs from the Korea Meteorological Administration and ECMWF show light westerly flow and partial cloud cover that should permit moderate radiative cooling after daytime highs near 23°C, yet boundary-layer mixing and weak warm advection introduce one- to two-degree uncertainty. Climatological May lows in Seoul average around 13°C, but the current pattern sits slightly above that baseline, keeping the modal outcomes clustered in the mid-teens. New 00Z and 12Z model updates expected within the next 24 hours will likely tighten the distribution ahead of the final observation period.