**Forecast models and official guidance point to a maximum temperature of 27–28°C in the Incheon/Seoul area on September 17, 2026, aligning with the market's heavy weighting on those two outcomes (57% and 36%).** Multiple sources, including KMA-aligned forecasts and international models, project a daytime high near 27–28°C (roughly 81°F) under partly cloudy to overcast skies, with easterly winds of 5–9 mph and negligible precipitation risk. This reflects typical mid-September climatology for the region, where average highs hover around 25–26°C as summer monsoon influences wane and autumn cooling begins, without active heatwaves or strong cold fronts. Recent stability in atmospheric conditions—high pressure and consistent easterly flow—has kept model runs steady, limiting upside or downside surprises. Hourly data show peaks in the afternoon around 27–28°C before gradual evening decline, with dew points in the mid-teens Celsius supporting moderate humidity and no extreme diurnal swings. The slim probabilities on 29°C+ or sub-26°C outcomes reflect low ensemble spread and the absence of unexpected developments such as clearer skies or stronger advection that could shift the maximum by a degree or more. Traders are effectively pricing the consensus from authoritative meteorological sources, with resolution hinging on official station readings from Incheon or Seoul later in the day.