Current forecast models point to a pre-monsoon regime over Hong Kong on May 20, with overnight minimum temperatures likely settling near 25°C under moderate humidity and variable cloud cover from South China Sea convection. The closely bunched probabilities for 24°C through 27°C stem from uncertainty over the precise onset of persistent southerly monsoon flow, which would limit radiative cooling and support higher lows near 26°C, versus lighter winds and clearer skies that could allow temperatures to dip toward 24°C. Regional sea surface temperatures averaging 27°C establish a warm thermal floor that makes readings below 23°C statistically rare in mid-May, while any increase in nocturnal cloudiness or wind shift could nudge the outcome higher. Revised numerical guidance over the next 48 hours will refine these distinctions ahead of market resolution.