Recent Japan Meteorological Agency outlooks project above-normal temperatures across eastern Japan through mid-August 2026, consistent with a strengthened Pacific high that limits nocturnal radiative cooling and keeps surface dew points elevated near 24–26°C. Short-range model guidance for August 8 shows overnight lows clustered around 25–27°C, with the precise minimum hinging on factors such as boundary-layer mixing, cloud cover from any passing weak trough, and Tokyo’s urban heat-island effect that can add 1–2°C compared with rural stations. The near-even split between the 26°C and 27°C outcomes on Polymarket therefore captures model spread in how efficiently heat will escape under persistently high humidity rather than any single dominant driver, while lower-probability bins below 25°C or above 28°C would require atypical clear-sky radiative cooling or unexpected advection of warmer air. Updated JMA and ensemble forecasts issued over the next 48 hours will likely narrow this range ahead of resolution.