**Recent forecasts from sources like timeanddate and AccuWeather point to overnight lows near 16–17°C for Seoul on June 17, 2026, under mostly cloudy conditions, aligning with the market’s tight clustering around 16°C-or-below (32%) and 20°C (27%).** This balance reflects uncertainty in short-range model guidance two days out. Key scientific drivers include limited radiational cooling from persistent cloud cover and high humidity typical of early East Asian summer monsoon transitions, which suppress nighttime temperature drops. Light winds and weak pressure gradients further moderate cooling, keeping minima close to the June climatological baseline of 18–21°C. Clearer skies or stronger northerly advection could push readings to 16°C or below, while stronger warm-air advection or increased cloud insulation might hold them near 20–21°C. KMA updates and fresh global model runs remain the primary near-term catalysts that could shift the narrow probability spread.