**Trader sentiment for the lowest temperature in Seoul/Incheon on September 8, 2026, centers on 19–20°C as the most likely range, with 19°C at 37.5% and 20°C at 43.5% implied probability.** These closely matched outcomes reflect current numerical weather prediction consensus showing overnight lows in that narrow band under stable late-summer conditions. Clear skies, light northeast to variable winds, and high pressure favor radiative cooling after daytime highs near 28–29°C, but limited cloud cover and dew points around 15–18°C prevent deeper drops. Official guidance such as Met Office forecasts point to a minimum near 20°C, while other model outputs and climatological analogs cluster around 19°C, creating the tight spread. Lower-probability tails (15°C or below at 16%) would require unexpected cooling from increased cloudiness or a shift in steering flow, which current runs do not support. Traders weigh the next GFS/ECMWF updates and any revised Korea Meteorological Administration guidance, as small changes in boundary-layer moisture or wind speed can shift the minimum by 1°C. Historical early-September minima average near 17–18°C, so the current warmer pattern supports the market’s focus on the upper end of typical variability.