**Persistent cloud cover, rain, and northeasterly flow limited overnight cooling in Tokyo on August 29, 2026, producing an official minimum of 21°C at the Tokyo Haneda Airport station used for market resolution.** Japan Meteorological Agency forecasts and numerical model guidance consistently projected overnight lows near 20–21°C under mostly cloudy to overcast conditions with light precipitation, consistent with observed temperatures that bottomed out around that level rather than dropping further or rising above it. Historical August climatology shows typical minima in the low-to-mid 20s °C, but the day's unsettled weather—driven by a frontal boundary and suppressed diurnal temperature range—kept values tightly clustered and anchored the daily low at the 21°C threshold. Trader consensus at 100% for 21°C reflects real-time alignment between forecasts, station observations, and the narrow uncertainty range in short-term guidance. The only realistic challenges would involve a post-event data revision from the official station or an unforeseen late-night temperature spike or plunge outside model consensus, both of which remain low-probability given the volume of confirming observations already in.