About this Market

Persistent heavy rainfall and northeasterly winds from an approaching low-pressure system or typhoon are suppressing daytime heating across Tokyo, keeping the September 21 maximum temperature tightly clustered around 24–26°C according to current model guidance. Cloud cover and elevated humidity limit solar warming, while stronger winds enhance mixing and evaporative cooling, shifting trader consensus toward the lower end of the historical late-September range of 27–29°C. Official Japan Meteorological Agency forecasts emphasize 100% precipitation probability with totals exceeding 80 mm, supporting the market’s narrow spread between 24°C and 26°C outcomes. Updated model runs and real-time observations on the day will determine the precise high.