Recent forecasts from models and the Korea Meteorological Administration indicate overnight lows in Seoul near 19–20°C for June 19, supporting the tight market split between those outcomes. Primary drivers include persistent cloud cover and elevated humidity from an advancing monsoon trough, which limit radiational cooling, alongside light winds that reduce mixing of cooler air near the surface. Ensemble guidance shows minor spread due to timing of any late-day showers and exact dew point values, with historical June averages around 18–20°C providing context. Updated model runs and official short-range forecasts expected in the next 24–48 hours will likely resolve the narrow gap between 19°C and 20°C.