About this Market

Persistent rain, extensive cloud cover, and northerly flow ahead of an approaching frontal system or typhoon influence are capping insolation and advecting cooler maritime air into the Tokyo region, keeping daytime maxima near 23–24 °C on September 20. High humidity and reduced solar heating differentiate these outcomes from the 25 °C scenario, while historical mid-September normals near 26–27 °C highlight the current anomaly. Japan Meteorological Agency guidance and ensemble model runs show only modest day-to-day shifts, sustaining tight market-implied odds between 23 °C and 24 °C. Updated short-range forecasts and observational data over the next 48 hours will refine the exact peak before resolution.