Current Japan Meteorological Agency forecasts indicate a strengthening high-pressure ridge over the Kanto region will bring clear skies, light southerly winds, and strong daytime solar heating to Tokyo on May 18. This setup favors peak temperatures reaching 28°C or higher, aligning with the market’s dominant 75% implied probability. Mid-May climatological averages for the Otemachi station hover near 23–25°C, so the projected warmth represents a notable positive anomaly driven by enhanced insolation and subsidence warming beneath the ridge. Ensemble guidance shows tight clustering around 28–30°C with limited spread, though modest model revisions ahead of the afternoon peak could still shift outcomes. Traders are monitoring the final JMA nowcasts and surface observations as resolution approaches.