**Trader sentiment for Seoul’s July 1 overnight low centers on 21°C and 22°C (combined ~72.5% implied probability) because short-range models and official guidance point to a narrow range around 20–22°C amid the early East Asian monsoon transition.** Recent forecasts from the Korea Meteorological Administration (KMA) and international sources such as BBC Weather and timeanddate show expected minimums near 20–21°C (68–70°F) under partly cloudy to overcast skies with light easterly winds and scattered shower chances. These conditions limit nighttime radiative cooling compared with clear, dry nights. Key scientific differentiators include cloud cover and humidity: increased moisture and cloudiness from monsoon flow trap long-wave radiation, keeping surface temperatures several degrees above the clear-sky radiative equilibrium that would otherwise produce lows near or below 19°C. Light winds reduce turbulent mixing that could otherwise bring slightly warmer air from aloft, while any overnight showers can further moderate cooling through latent heat release and increased humidity. Historical early-July climatology for Seoul shows average lows near 22–23°C, but the current setup—with building humidity and precipitation probabilities—favors values on the lower side of that range. New model runs and KMA updates in the final 48 hours before July 1 will likely determine whether the market shifts toward 21°C or 22°C.