Recent heavy rainfall across the Kanto region on September 20–21 has suppressed daytime heating, but official Japan Meteorological Agency guidance and ensemble models now indicate partly cloudy to scattered shower conditions for Tokyo on the 22nd, with daytime maxima most likely reaching 29–31 °C. Light northwest winds and moderate humidity levels support modest warming once clouds break, though lingering moisture could cap peaks near 30 °C. This range sits well above the late-September climatological normal of roughly 26 °C, reflecting the influence of a transient ridge and reduced cloud cover relative to the preceding days. Traders have clustered implied probabilities on 30 °C and 31 °C because small differences in timing of showers versus clearer intervals will determine whether the daily maximum exceeds or falls short of those thresholds. Updated short-range model runs and surface observations over the next 48 hours remain the key variables that could shift the distribution.