**Recent model consensus from sources including the Japan Meteorological Agency and global ensembles points to a minimum temperature in Tokyo on September 28, 2026, centered in the 21–22°C range.** Persistent cloud cover, high humidity (often above 85–95%), and light variable winds associated with a lingering moist airmass are limiting nocturnal radiational cooling, keeping overnight lows elevated relative to clear-sky climatology for late September. Forecasts show widespread light rain or drizzle through the period, with daytime highs near 23–25°C transitioning to overnight values around 21°C. This setup favors 22°C as the modal outcome in trader pricing (41.5% implied probability), followed closely by 23°C (30%) and 21°C (23%), reflecting tight model agreement on minimal day-to-day variability. Lower probabilities assigned to 20°C or below (under 7% combined) align with the absence of any strong cold-air advection or clear-sky conditions that would allow greater cooling. Upcoming JMA and ECMWF updates over the next 24–48 hours remain the key near-term catalysts that could refine these market-implied odds.