Japan Meteorological Agency forecasts and ensemble models indicate overnight lows in Tokyo around 23–24°C for August 17 under the influence of the strengthened Pacific High, which sustains warm, humid maritime air and limits radiative cooling. High dew points, widespread cloud cover with possible scattered showers or thunderstorms, and the urban heat-island effect from dense infrastructure further suppress temperature drops below the seasonal normal of about 24°C. Trader sentiment clusters tightly on these values because small differences in forecast timing of rainfall or brief clear intervals could shift the minimum by 1°C, while stronger subsidence or marine air intrusions remain unlikely without major synoptic changes. Updated model runs and evening observations will refine probabilities ahead of resolution.