Forecast models from the Japan Meteorological Agency and ensemble guidance indicate a most-likely overnight low near 23–25 °C for Tokyo on August 5 under cloudy to partly cloudy skies with light winds and possible showers, producing the tight clustering of market-implied odds around 22–25 °C. Persistent influence of the strengthened Pacific High sustains above-normal seasonal temperatures across Honshu, limiting nocturnal radiative cooling amid high humidity and urban heat-island effects that typically keep minimums from falling below 21 °C. Short-term variability in afternoon convection timing and cloud cover introduces modest uncertainty between the 22 °C and 25 °C bands, while historical August climatology for the Kanto region places average lows near 24 °C. Traders weigh these factors against the next high-resolution model runs expected before resolution.