**Persistent southwest monsoon flow and an active trough of low pressure are keeping Hong Kong under widespread cloud cover and periods of rain through June 16, 2026, which narrows the diurnal temperature range and caps overnight lows near 25–27 °C.** Official guidance from the Hong Kong Observatory indicates rain on the 16th with daytime maxima of 26–29 °C; the associated moisture and reduced insolation typically prevent strong radiative cooling after sunset, holding minimums close to the daily mean. Seasonal outlooks already flag above-normal temperatures for the June–August period, yet the immediate synoptic pattern favors a modest cooling effect from persistent cloud and showers rather than clear-sky radiational lows. Model consensus shows little spread in this short-range window, with ensemble guidance clustering around a 26 °C minimum; any break in the rain or shift in wind direction could allow a 1–2 °C drop, while continued heavy precipitation would favor the upper end of the distribution. Traders are therefore pricing the tight 25–27 °C cluster as the highest-probability outcome given current steering patterns and boundary-layer moisture.