**Forecast models for Incheon/Seoul on August 29, 2026, converge on overnight lows near 24–25 °C, consistent with the market’s tight 24 °C (36.5 %) versus 25 °C (46.0 %) pricing.** Official guidance from the Korea Meteorological Administration and Met Office indicates a minimum of 24 °C under partly cloudy skies with light westerly winds and scattered showers, while other ensembles show slightly warmer readings if cloud cover reduces nocturnal radiative cooling. Typical late-August climatology places the average minimum near 22–23 °C, but recent days have featured elevated humidity (often >90 %) and residual moisture from prior precipitation, which limits temperature drops by suppressing clear-sky longwave radiation loss. Light winds (3–6 kt) reduce turbulent mixing, allowing the surface layer to cool more efficiently in clearer pockets, yet any increase in low-level cloud or timing of showers can add 1 °C of warmth by dawn. The narrow spread between 24 °C and 25 °C therefore reflects modest model disagreement on exact cloud timing and boundary-layer moisture rather than large-scale synoptic shifts. With resolution expected within hours of the overnight minimum, updated model runs and observational trends will determine which outcome traders ultimately favor.