With the dominance of a dry northeast monsoon over southern China for most of 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 per cent above the normal of 145.8 hours. Only 4.2 millimetres of rainfall were recorded in the month, about 13 per cent of the normal of 33.2 millimetres. The monthly mean relative humidity of 59 per cent was 15 per cent below the normal of 74 per cent 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 January 1. Under the influence of the northeast monsoon, it was generally fine from January 3 to 9, apart from a few light rain patches on the night of January 4 and the morning of January 5.

     With the arrival of an intense winter monsoon on the night of January 9, the weather was cold on the mornings of the following three days. It was very dry with relative humidity across the territory remaining at 30 per cent or below during the day on January 12. The daily minimum relative humidity of 9 per cent 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 gradually turned milder from January 13 to 15. Temperatures at the Observatory peaked at 22.3 degrees on the afternoon of January 15, the highest for the month.

     Under the influence of a dry northeast monsoon, it was generally fine with cool mornings from January 16 to 20. 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 over the following three days. With the band of clouds thinned out, it was generally fine on January 24 and 25.

     A cold front moved across the coast of southern China on the morning of January 26. 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 progressively turned cold that night. Under the influence of the associated intense winter monsoon, the weather became generally fine and very dry with cold mornings on January 27 and 28. The temperatures at the Observatory dropped to a minimum of 10.6 degrees on the morning of January 27, the lowest of the month. The monsoon was gradually replaced by a fresh to strong easterly airstream on January 29. 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 January 30, 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 Table 1. Monthly meteorological figures and departures from normal for January are tabulated in Table 2.

Ends/Tuesday, February 4, 2025
Issued at HKT 16:00

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