Latest numerical weather prediction models from agencies including the Japan Meteorological Agency show Tokyo’s June 15 maximum temperature centered near 21–22 °C, producing the tightest clustering of trader-implied probabilities at 36.5 % and 32.5 %. Ensemble spreads remain narrow because the dominant synoptic pattern features modest onshore flow and limited daytime insolation, keeping surface heating modest relative to early-summer climatology. Small divergences between runs arise mainly from timing of cloud cover and boundary-layer mixing; a modest increase in afternoon sunshine or reduced wind would favor the 23 °C outcome now at 17 %, while greater marine influence would support the 20 °C tier at 10.5 %. With resolution less than 24 hours away, traders are weighting the most recent high-resolution model cycles and observed trends over longer-range seasonal signals.