With the dominance of dry northeast monsoon over southern China for most of the time in the month, January 2025 was marked by dry and sunny weather in Hong Kong. The monthly total sunshine duration amounted to 222.3 hours, about 52 percent above the normal of 145.8 hours. 4.2 millimetres of rainfall were recorded in the month, only about 13 percent of the normal of 33.2 millimetres in the month. The monthly mean relative humidity of 59 percent was 15 percent below the normal of 74 percent and the third lowest on record for January. The month was also slightly warmer than usual with the mean temperature of 17.1 degrees, 0.6 degrees above the normal of 16.5 degrees.

Affected by an easterly airstream, the weather of Hong Kong was mainly cloudy on the first two days of the month, with one or two light rain patches on 1 January. Under the influence of the northeast monsoon, it was generally fine on 3 – 9 January apart from a few light rain patches on the night of 4 January and on the morning of 5 January. 

With the arrival of an intense winter monsoon on the night of 9 January, the weather was cold on the mornings of the following three days. It was very dry with the relative humidity over the territory staying at 30 percent or below during the day on 12 January. The daily minimum relative humidity of 9 percent at Chek Lap Kok was the second lowest on record for January since the station was established in June 1997. As the monsoon was replaced by an easterly airstream, the weather turned milder gradually on 13 – 15 January. The temperatures at the Observatory rose to a maximum of 22.3 degrees on the afternoon of 15 January, the highest of the month. 

Under the influence of a dry northeast monsoon, it was generally fine with cool mornings on 16 – 20 January. Affected by a fresh to strong easterly airstream and a band of clouds covering the coast of Guangdong, local weather became cloudier with a few rain patches in the following three days. With the band of clouds thinning out, it was generally fine on 24 – 25 January.

A cold front moved across the coast of southern China on the morning of 26 January. Locally, it was mainly cloudy with one or two rain patches on that day. With the strengthening of the northerlies, the weather of Hong Kong became cold progressively that night. Under the influence of the associated intense winter monsoon, it turned generally fine and very dry with cold mornings on 27 – 28 January. The temperatures at the Observatory dropped to a minimum of 10.6 degrees on the morning of 27 January, the lowest of the month. The monsoon was gradually replaced by a fresh to strong easterly airstream on 29 January. While it was cloudy at first, the weather turned fine and very dry during the day. With a band of clouds setting in over the coast of Guangdong, the weather turned cloudy on the night of 30 January and there were one or two rain patches on the last day of the month.

There was no tropical cyclone over the South China Sea and the western North Pacific in January 2025.

Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.4.  Monthly meteorological figures and departures from normal for January are tabulated in Table 2.