**Persistent summer heatwave conditions across the Seoul-Incheon region are the primary driver behind the market's strong preference for a 27°C or 28°C overnight low on August 5.** Current forecasts and recent observations point to continued high daytime maxima of 35–37°C through early August, with the associated high humidity and urban heat retention preventing substantial nighttime cooling. This setup typically produces minimum temperatures in the mid-to-upper 20s Celsius, consistent with the market-implied probabilities where 27°C leads at 42% and 28°C follows at 29.5%. Official monitoring from the Korea Meteorological Administration and extended outlooks highlight a stable high-pressure pattern with light winds and limited cloud cover, which favors elevated lows compared to the August climatological average of around 22–24°C. Recent days have already shown overnight minima near 26°C amid the heatwave, and short-range guidance through August 7 maintains similar conditions without significant frontal passages or heavy rainfall that could enhance radiative cooling. Traders appear to be weighting the consensus from dynamical models and persistence of the current synoptic regime, which supports the clustering around 27–28°C while assigning low odds to cooler outcomes below 25°C or warmer extremes above 29°C. Updated forecast runs and any shifts in the steering flow will be key near-term variables as the market approaches resolution.