Uncertainty in short-term forecast models for overnight radiative cooling under the prevailing subtropical high pressure over the South China Sea is the primary driver keeping the lowest temperature on May 19 tightly contested among 24–26°C outcomes. Mid-May climatology in Hong Kong typically produces minimums of 24–26°C, modulated by humidity levels, light variable winds, and partial cloud cover that limit clear-sky cooling. Recent ensemble guidance from regional models shows minor disagreements on the strength of southerly flow, which could either suppress or enhance the nocturnal drop by a degree or two. Traders are weighting the next Hong Kong Observatory updates and fresh ECMWF/GFS runs, as these will clarify whether conditions favor the central 25°C band or edge toward the warmer or cooler tails.