Recent Japan Meteorological Agency forecasts highlight persistent cloud cover and scattered showers over Tokyo on June 21, stemming from the ongoing tsuyu rainy season, as the primary driver capping trader-implied highs near 25–26 °C. These conditions reduce solar insolation and enhance evaporative cooling, preventing the stronger afternoon heating typical of clearer early-summer days when maxima often reach 28–30 °C. Seasonal outlooks note above-average temperatures overall, yet short-term model consensus emphasizes variable shower timing and intensity as key uncertainties that could shift the daily peak by 1–2 °C. This genuine forecast spread explains the closely matched market probabilities clustered around historical June averages.