Current forecasts from the Korea Meteorological Administration and ensemble models indicate the September 1 overnight minimum in the Incheon-Seoul area will likely settle between 21–23 °C, aligning with market-implied odds clustered around those values. Persistent cloud cover and widespread rainfall through the period—driven by a slow-moving frontal system delivering 30–80 mm across the capital region—limit nocturnal radiative cooling and compress the diurnal range. Light winds and high humidity further suppress temperature drops, keeping readings several degrees above early-September climatological averages near 18–20 °C. Minor model spread in rain timing and cloud persistence accounts for the probability distribution across adjacent outcomes, with clearer breaks potentially allowing a dip toward 21 °C and heavier overcast favoring the upper end of the range.