**Recent typhoon activity and associated cloud cover and rainfall are the main near-term drivers shaping market-implied odds for Tokyo’s lowest temperature on September 23.** A powerful typhoon (Dujuan/25号) tracked close to eastern Japan on September 20–21, delivering heavy rain, strong winds, and linear rain bands that elevated flood and landslide risks across the Kanto region including Tokyo. This system has left lingering overcast skies, elevated humidity, and suppressed daytime heating heading into the 23rd. Official and model guidance now converge on daytime highs of roughly 24–27 °C (76–81 °F) and overnight/early-morning lows of 21–22 °C (70–72 °F) under mostly cloudy to overcast conditions with light rain chances. These values align closely with the leading 22 °C outcome (47.5 % implied probability) and support the elevated odds on 21 °C and 23 °C bins. The 17 °C-or-below market (25.5 %) reflects residual uncertainty around post-storm cooling or localized heavy-rain effects that could pull the minimum lower, while the 27 °C-or-higher outcome (23.5 %) remains a long-shot tail risk requiring unexpectedly rapid clearing and warming. Climatologically, late-September Tokyo minima average near 19 °C, but the current disturbed pattern favors a slightly milder floor. Key upcoming updates include the next Japan Meteorological Agency (JMA) forecast runs and any revisions to steering flow or residual moisture, which traders will watch closely before resolution.