Recent Japan Meteorological Agency forecasts place Tokyo’s maximum temperature on May 17 near 28 °C at the official Otemachi station, driven by a persistent high-pressure ridge that favors southerly warm advection and strong afternoon solar heating under mostly clear skies. Numerical weather prediction models show tight agreement on this value, consistent with mid-May climatology for the Kanto plain where daily highs typically range from 24 °C to 28 °C. The overwhelming market-implied probability for exactly 28 °C reflects this forecast convergence and the limited time remaining for major revisions before the daily maximum is recorded. A sudden increase in cloud cover, stronger northerly flow, or an earlier sea-breeze onset could cap temperatures one degree lower, while any delay in the ridge breakdown might allow a brief push toward 29 °C.