With the northeast monsoon over the south China coast much weaker than normal, the weather of Hong Kong was exceptionally warm in the first half of December 2023. While Hong Kong was affected by an intense winter monsoon in the second half of the month, December was overall still warmer than usual in Hong Kong. The monthly mean temperature of 19.1 degrees was 0.9 degrees above the normal figure of 18.2 degrees and one of the ninth highest on record for December. The month was also much drier than usual with a total rainfall of 0.9 millimetres, only about three per cent of the normal figure of 28.8 millimetres. The annual total rainfall of 2 774.5mm was about 14 per cent above the annual normal of 2 431.2mm.
Affected by the northeast monsoon, apart from a few light rain patches, the weather of Hong Kong was mainly cloudy and dry with sunny intervals during the day on the first four days of the month. Under light wind conditions and with the clouds thinning out, the local weather became generally fine on December 5. While there were a few light rain patches and the visibility was relatively low in some areas on the morning of December 6, the weather turned fine and dry in the afternoon with the setting in of a dry northeast monsoon and remained so the next two days. It was also very dry during the day on December 7. Under the influence of a relatively humid easterly airstream, the weather turned cloudier on December 9.
Apart from cloudier weather and a few rain patches on the morning of December 11, it was generally fine and rather warm from December 10 to 12. With abundant sunshine, the temperature at the Observatory rose to a maximum of 28.7 degrees on the afternoon of December 12, the highest of the month and one of the highest maximum temperature on record for December.
Under the influence of an easterly airstream and with a band of clouds covering the coast of Guangdong, the weather of Hong Kong turned mainly cloudy with a few rain patches on December 13 and 14. With the moderation of the easterly airstream, it was warm with sunny periods during the day the next day. Meanwhile, a cold front formed over central China and moved across the coast of Guangdong on the morning of December 16. Locally, winds strengthened from the north with a few rain patches in the morning. Temperatures fell appreciably with sunny intervals during the day. Affected by the associated winter monsoon and with a band of clouds covering southern China, the weather of Hong Kong turned cloudy and cold on December 17. It was mainly cloudy with cool mornings on December 18 and 19.
Affected by an intense replenishment of the winter monsoon, it was mainly cloudy and cold in Hong Kong from December 20 to 23. With a rainband moving across the coastal areas of Guangdong, there were a few rain patches in Hong Kong on the morning of December 23. The temperature at the Observatory dropped to a minimum of 8.1 degrees that morning, the lowest of the month. With the clouds thinning out, the weather of Hong Kong became fine and dry from December 24 to 26. It was also cold on the mornings of December 24 and 25. Moreover, there were frost reports in Tai Po and Ta Kwu Ling on the morning of December 24. As the winter monsoon moderated, apart from a few light rain patches, local weather turned milder gradually with sunny periods during the day from December 27 to 29. Under light wind conditions, the weather was dry and rather warm with sunny periods during the day on the last two days of the month. The visibility was also rather low in some areas. The visibility at Chek Lap Kok once fell below 2 000 metres on the morning of December 31. The temperatures at the Observatory rose to a maximum of 25.7 degrees on the afternoon of December 31, making it the warmest New Year's Eve on record.
One tropical cyclone occurred over the South China Sea and the western North Pacific in December 2023.
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 December are tabulated in Table 2.
