**Trader sentiment for the lowest temperature in Hong Kong on August 4 centers on 25–26°C as the most probable range, reflecting typical subtropical summer conditions and official outlooks.** Hong Kong Observatory seasonal and monthly forecasts for August 2026 indicate normal to above-normal temperatures, consistent with the long-term warming trend and current ENSO influences, with near-normal rainfall expected. Short-range guidance shows showers or overcast skies on August 4 with overnight lows near 26°C and daytime highs of 29–31°C, aligning closely with climatological August minima around 27°C that can moderate to 25–26°C under cloud cover or precipitation. Scientific factors include high humidity, limited nocturnal radiative cooling in the urban heat island, and the South China Sea monsoon trough favoring warm, moist air masses. The elevated probability on 21°C or below (19.5%) captures tail risk from heavier showers or model variability, while warmer outcomes above 27°C remain less favored given the absence of strong warming signals in early-August guidance. Updated HKO briefings and model runs over the next 48 hours will be key for refining these market-implied odds.