Recent Japan Meteorological Agency forecasts and ensemble model guidance point to a Tokyo overnight minimum near 21°C for June 14, 2026, aligning with the market’s 78% implied probability for that outcome. Early-summer tsuyu conditions feature elevated humidity, variable cloud cover, and modest nocturnal radiative cooling that anchors lows within the 19–21°C climatological band. Supporting observations show no strong cold-air advection or high-pressure buildup capable of driving readings below 20°C, while limited forecast spread across guidance reinforces trader consensus. A realistic deviation to 20°C or lower would require an unexpected late-evening frontal passage or station-specific measurement anomaly, though current data indicate low likelihood outside the narrow 20–21°C range.