Traders assign 96% implied probability to a 25°C minimum in Tokyo on August 18 because official forecasts from the Japan Meteorological Agency and international models consistently project overnight lows near 23–25°C under partly cloudy conditions with light winds and high humidity typical of mid-August climatology. Recent model runs show stable steering patterns with no strong frontal systems or enhanced radiative cooling expected to push readings lower, while urban heat island effects in the Tokyo metro area further support minimums at or above the seasonal normal of 23–24°C. The slim 4% chance for 24°C or below reflects residual forecast uncertainty in boundary-layer moisture and localized cloud cover, scenarios that would require faster-than-expected clearing or atypical advection of cooler maritime air to materialize before dawn observations finalize the daily minimum.