Recent forecasts from meteorological agencies indicate Tokyo's minimum temperature on June 15 will likely fall in the 17–19°C range amid the early tsuyu rainy season, with widespread cloud cover, showers, and northeasterly flow limiting nocturnal radiative cooling. Model consensus shows overnight lows near 18°C as the most probable outcome, consistent with current observations of seasonal baselines around 21°C and recent early-June readings dipping to 16–18°C under similar synoptic patterns. Trader emphasis on 18°C reflects high confidence in stable maritime air masses and forecast reliability within 24 hours of resolution, though minor shifts in precipitation timing or wind could push values toward 17°C or 19°C. Updated model runs and official Japan Meteorological Agency guidance remain the key near-term catalysts.