Recent Japan Meteorological Agency forecasts for Tokyo on June 15 project rainy conditions with a maximum near 20–22°C under persistent cloud cover, directly supporting the market's tight clustering where 22°C holds 34.5% implied probability and 21°C follows at 31.5%. The primary driver is reduced solar insolation from widespread precipitation and stratus clouds during the early tsuyu rainy season, which limits daytime heating compared to clearer analogs. Minor model differences in rain timing and intensity create the narrow spread among leading outcomes, while historical June baselines around 26°C highlight how this synoptic pattern suppresses temperatures. Updated JMA guidance and ensemble runs expected overnight will likely refine the final resolution.