Recent forecasts from the Japan Meteorological Agency and global models indicate a frontal system and associated low-pressure influence will bring persistent cloud cover, light rain, and onshore flow to the Kanto region on September 28, limiting daytime solar heating and suppressing maximum temperatures. This setup favors highs near 23–25°C, with the tight clustering of market odds around 25–26°C reflecting uncertainty in exact cloud timing and any brief clearing that could allow modest warming. Cooler maritime air advection and evaporative cooling from precipitation further differentiate the 24°C outcome from higher bins, while historical late-September baselines near 26°C provide context for the downward shift. Updated model runs and the official JMA Tokyo observation will resolve the market.