Recent ensemble forecasts from the Japan Meteorological Agency and global models have converged on an overnight low of 19°C for Tokyo on June 17, supported by a stable subtropical high-pressure system, light southerly flow, and partly cloudy conditions that limit radiative cooling. This setup keeps minimum temperatures near or slightly above the mid-June climatological average of 17–19°C, with above-normal seasonal warmth from an expanded Pacific High reducing the potential for sharper nocturnal drops. Traders have priced this outcome at near-certainty because short-range guidance shows high consistency within a narrow 18–20°C band, though modest shifts in cloud cover, timing of any showers, or localized wind changes could still nudge the observed low by 1°C before final measurement at official stations.