Latest JMA and global model runs indicate Tokyo’s August 21 maximum will most likely fall between 30–32 °C under mostly cloudy skies and scattered showers or thunderstorms that reduce insolation and cap afternoon heating. A persistent subtropical ridge supports warm southerly advection, yet increased cloud cover and higher humidity—typical of late-summer conditions—limit the potential for stronger surface warming compared with clearer days earlier in the week. Ensemble spreads remain modest around the 31 °C mark, producing the tight clustering of market-implied probabilities across the 30–32 °C outcomes while assigning only low odds to extremes outside that range.