**Persistent high-pressure patterns and elevated humidity are anchoring overnight lows near 22–23°C in Tokyo for August 4.** The Japan Meteorological Agency’s early August outlook and short-range guidance show mostly cloudy conditions under an expanded Pacific High, which suppresses radiative cooling while maintaining dew points that limit temperature drops. Historical climatology places Tokyo’s early-August minimums around 24°C, but recent model runs and the seasonal forecast of above-normal temperatures have tempered expectations slightly, favoring a narrow range just below that baseline. AccuWeather’s extended guidance similarly projects overnight lows of roughly 22–26°C, with the tightest clustering around 22–23°C. These conditions explain why trader-implied probabilities concentrate on 22°C and 23°C, reflecting both current synoptic stability and the narrow uncertainty window two days before the observation period.