Hong Kong Observatory forecasts for May 18 point to a 25–29°C range under mainly cloudy skies with scattered showers and southeast winds, anchoring trader consensus around 24–25°C as the most probable overnight minimum. A persistent trough of low pressure over the northern South China Sea sustains elevated relative humidity of 75–95 percent, which suppresses nocturnal radiative cooling and favors the higher end of the range. Light southerly flow and urban heat-island effects further limit sharp temperature drops, while any brief clearing or reduced cloud cover could allow the minimum to edge toward 24°C. Historical mid-May data show typical lows clustering between 24–25°C during the pre-monsoon transition, with model refinements from the next HKO bulletin likely to clarify the final balance between these competing influences.