Recent short-range forecasts from the Korea Meteorological Administration and global models indicate Seoul overnight lows near 20–21°C for June 18, supporting the near-even market split between those outcomes. Key differentiating factors include the degree of overnight cloud cover, which modulates radiative cooling, and light wind speeds that limit mixing of warmer air aloft. Clearer conditions favor the lower end near 20°C by allowing greater surface heat loss, while increased humidity or southwesterly flow could hold temperatures closer to 21°C. Typical mid-June climatology places minimums in the 18–22°C range, and the tight probabilities reflect uncertainty in the precise timing of any clearing or subtle advection changes ahead of resolution.