Official forecasts from the Hong Kong Observatory and numerical models point to an overnight minimum near 27°C on August 20, driven by persistent cloud cover, scattered showers, and thunderstorms that limit nocturnal radiative cooling in Hong Kong’s subtropical climate. High humidity combined with light easterly winds keeps surface temperatures elevated, consistent with late-summer patterns where historical August lows average around 27°C amid a seasonal outlook for normal to above-normal temperatures. These conditions explain the market’s concentration on 27°C (47%) and 28°C (29.5%), with modest probability on 26°C reflecting uncertainty in shower timing and intensity that could allow slightly greater cooling. Updated model runs and observatory briefings over the next 24 hours will refine resolution criteria tied to official minimum readings.