With less moisture in the lower atmosphere over the coast of southern China, December 2024 was much drier than usual in Hong Kong. Only traces of rainfall were recorded in the month and it was one of eleven Decembers with just traces of rainfall since records began in 1884. The annual total rainfall of 2 309.7 millimetres was about 5 percent below the annual normal of 2 431.2 millimetres. The monthly mean temperature was 18.5 degrees, 0.3 degrees above the December normal of 18.2 degrees.

The weather of Hong Kong was fine and dry on the first two days of the month. Under the influence of an easterly airstream and the subsequent northeast monsoon, apart from cloudy periods in the morning and at night, it was mainly fine during the day on 3 – 7 December. With the strengthening of the monsoon and a band of clouds covering the coast of Guangdong, it became cloudier with cool mornings on 8 – 9 December. The northeast monsoon moderated and the weather turned warmer with sunny periods on 10 – 11 December. The temperatures at the Observatory rose to a maximum of 25.2 degrees on the afternoon of 11 December, the highest of the month.

Under the influence of a dry northeast monsoon, there were sunny periods with cool mornings on 12 – 17 December. There were also a few light rain patches on the night of 15 December. Affected by a replenishment of the winter monsoon, while it was cloudy in the morning, the weather turned fine and dry on the afternoon of 18 December and remained so on the next four days. The temperatures at the Observatory dropped to a minimum of 11.9 degrees on the morning of 20 December, the lowest of the month. Under clear skies, the temperatures in the New Territories were significantly lower than those in the urban areas on the mornings of 19 – 21 December.

Under the influence of a broad band of clouds associated with tropical depression Pabuk over the southern part of the South China Sea, local weather turned mainly cloudy on 23 – 27 December. There were also a few light rain patches on 23, 25 – 26 December. Affected by a replenishment of the northeast monsoon, while it was cloudy at first, the weather turned fine and dry during the day on 28 December and remained so until the end of the month. With the setting in of a fresh easterly airstream, the weather turned cloudy with a few light rain patches later on 31 December. 　

One tropical cyclone occurred over the South China Sea and the western North Pacific in December 2024.

Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.3.  Monthly meteorological figures and departures from normal for December are tabulated in Table 2.

Warnings and Signals issued in December 2024

Table 1.1   Strong Monsoon Signal

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
14 / 12	0130	15 / 12	0745
28 / 12	0615	28 / 12	0915

Table 1.2   Fire Danger Warnings

Colour	Beginning Time		Ending Time
	Day/Month	HKT	Day/Month	HKT
Yellow	1 / 12	0600	1 / 12	2030
Yellow	7 / 12	0600	8 / 12	2330
Red	14 / 12	0600	22 / 12	2315
Yellow	26 / 12	0945	26 / 12	1900
Red	28 / 12	0600	29 / 12	0600
Yellow	29 / 12	0600	29 / 12	2050
Red	31 / 12	0600	31 / 12	2145

Table 1.3   Cold Weather Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
19 / 12	1620	20 / 12	1030
20 / 12	2230	21 / 12	0940
21 / 12	1620	22 / 12	0940

Table 2   Figures and Departures from Normal - December 2024

Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	20.8 degrees C	0.4 degrees above normal
Mean Air Temperature	18.5 degrees C	0.3 degrees above normal
Mean Daily Minimum Air Temperature	16.5 degrees C	0.3 degrees above normal
Mean Dew Point Temperature	10.3 degrees C	2.1 degrees below normal
Mean Relative Humidity	60 %	10 % below normal
Mean Cloud Amount	54 %	3 % below normal
Total Rainfall	Trace	28.8 mm below normal
Number of hours of Reduced VisibilityΔ	8 hours	168.1 hours below normal§
Total Bright Sunshine Duration	199.5 hours	37.9 hours above normal
Mean Daily Global Solar Radiation	13.39 Megajoule / square metre	2.48 Megajoule above normal
Total Evaporation	96.6 mm	15.7 mm above normal

Remarks :	All measurements were made at the Hong Kong Observatory except sunshine, solar radiation and evaporation which were recorded at King's Park Meteorological Station and visibility which was observed at the Hong Kong International Airport.
Δ	The visibility readings at the Hong Kong International Airport are based on hourly observations by professional meteorological observers in 2004 and before, and average readings over the 10-minute period before the clock hour of the visibility meter near the middle of the south runway from 2005 onwards. The change of the data source in 2005 is an improvement of the visibility assessment using instrumented observations following the international trend. Before 10 October 2007, the number of hours of reduced visibility at the Hong Kong International Airport in 2005 and thereafter displayed in this web page was based on hourly visibility observations by professional meteorological observers. Since 10 October 2007, the data have been revised using the average visibility readings over the 10-minute period before the clock hour, as recorded by the visibility meter near the middle of the south runway.
*   Departure from 1991 - 2020 climatological normal, except for number of hours of reduced visibility
§   Departure from mean value between 1997 and 2023

Remarks :

Extremely high: above 95th percentile Above normal: between 75th and 95th percentile Normal: between 25th and 75th percentile Below normal: between 5th and 25th percentile Extremely low: below 5th percentile Percentile and 5-day running average values are computed based on the data from 1991 to 2020