Latest Japan Meteorological Agency forecasts and ensemble runs from the European Centre for Medium-Range Weather Forecasts project Tokyo’s overnight low on May 18 near 18–19 °C, driven by a stable high-pressure ridge yielding partly cloudy skies and light northerly flow that limits radiative cooling. This consensus, consistent with mid-May climatology of 16–18 °C daily minima at Otemachi station, supports the tight clustering around the 17 °C, 18 °C, and 19 °C outcomes. Key variables still in play include any late-evening cloud cover that could trap heat and push readings toward 20 °C, versus clearer intervals allowing brief dips near 17 °C, with final resolution hinging on the official minimum recorded between 00:00 and 06:00 JST.