Heavy rain forecast for Guangzhou on August 26, with models indicating showers or thunderstorms, stands as the main driver of closely matched market odds clustered around 23–29°C. Persistent cloud cover and precipitation suppress daytime heating while promoting evaporative cooling and reduced nocturnal radiative losses, often lowering minimum temperatures by 1–3°C relative to clear-sky baselines in subtropical monsoon climates. Official guidance from regional meteorological centers shows overnight lows near 25°C under these conditions, consistent with climatological August averages of 25–26°C but sensitive to exact rainfall timing and intensity. Model spread on storm track and moisture convergence introduces genuine uncertainty, keeping probabilities balanced across several temperature bins as traders weigh incoming forecast updates.