**Persistent extreme heatwave conditions across South Korea are the dominant driver positioning 27–28°C as the leading outcomes for Seoul (Incheon)’s overnight low on August 7, 2026.** Official Korea Meteorological Administration (KMA) guidance and aligned global models indicate minimal overnight cooling under a strong high-pressure regime, with light winds, high humidity (often 70–85%), and clear to partly cloudy skies limiting radiative heat loss. This produces “tropical night” patterns where lows remain at or above 25°C, well above the long-term early-August climatological average of 22–24°C. Recent record-setting daytime highs (including a national peak of 42.5°C on August 2) and widespread heatwave/emergency advisories extending through August 6–7 have reinforced trader expectations of sustained warmth. Urban heat-island effects in the Seoul-Incheon corridor further suppress nighttime minima. Short-range KMA updates and model consensus show little relief expected before mid-month, keeping market-implied probabilities concentrated on 27°C (41.5%) and 28°C (52.0%), with only modest weight on 29°C or 26°C. Updated forecast runs in the next 24–48 hours will be the key near-term catalyst.