**Recent forecasts from sources like the Japan Meteorological Agency (JMA), Yr.no, and private models show Tokyo's overnight minimum on August 24, 2026, centered around 24–26 °C, with the bulk of guidance clustering near 25 °C.** This aligns with the tight market spread (25 °C at 43.5 % implied probability, 26 °C at 34 %), as traders weigh ensemble outputs and observed trends from the prior week, when minima hovered between 23–25 °C amid variable cloud cover and light southerly flow. Primary drivers include the urban heat island effect, which elevates nighttime temperatures by 1–3 °C relative to rural baselines through retained heat from concrete and reduced ventilation. High humidity (often 80–95 % overnight) and partial cloud cover suppress radiative cooling, while light southerly winds advect warmer maritime air. Recent scattered showers and lingering moisture from mid-August systems have kept dew points elevated near 24 °C, limiting the diurnal temperature range. Clearer spells could allow slightly more cooling toward 24–25 °C, whereas persistent low-level clouds or stronger southerly advection would favor 26 °C. Differentiation between the leading outcomes hinges on small-scale boundary-layer details—exact cloud fraction during the 02:00–06:00 local minimum window, wind speeds under 3 m/s versus 4–6 m/s, and any late-day shower timing—that produce 1 °C spreads across models. Historical August normals for Tokyo minima are near 23 °C, but the current pattern of above-average warmth and humidity supports the market's lean toward the upper end of that range. Updated JMA guidance and new model runs over the next 24–48 hours will likely refine the narrow 25–26 °C contest.