Recent forecasts from the Japan Meteorological Agency and global models indicate overnight lows in Tokyo on August 13 centering on 22–24°C, driven by persistent cloud cover and scattered showers that limit nocturnal radiative cooling. High humidity—typical for mid-August—reduces the temperature drop after sunset by trapping heat near the surface, while any rain further moderates extremes through evaporative effects and reduced clear-sky cooling. Historical baselines show average August minimums near 24°C, but variable steering patterns and model spread on precipitation timing create the tight clustering around 23°C (leading at 44.5%) versus 24°C. Updated JMA guidance and ensemble runs over the next 24–48 hours will likely narrow the range ahead of market resolution.