Recent forecasts from the Japan Meteorological Agency place Tokyo’s May 17 overnight minimum near 16–17 °C under partly cloudy skies and light northerly flow across the Kanto Plain. This range aligns with mid-May climatology, where average lows sit between 15 °C and 18 °C, modulated by the strength of the subtropical high and any residual marine air intrusion. Ensemble model runs show tight agreement on the timing of radiative cooling after sunset, but small differences in cloud cover or wind speed could shift the exact reading by 1 °C. With leading outcomes closely matched, traders are pricing the genuine uncertainty inherent in short-term temperature resolution rather than any single dominant driver.