4 January 2023

With stronger than normal northeast monsoon affecting southern China in the month, the weather of Hong Kong was colder than usual in December 2022. The monthly mean temperature was 16.6 degrees, 1.6 degrees below the normal figure of 18.2 degrees. The monthly total rainfall was 25.7 millimetres, about 11 percent below the normal figure of 28.8 millimetres. The annual total rainfall of 2205.4 millimetres in 2022 was about 9 percent below the annual normal of 2431.2 millimetres.

Under the influence of an intense northeast monsoon, the weather of Hong Kong was cloudy and rather cool on the first day of the month. The weather became brighter with cool morning the next day. With the moderation of the northeast monsoon, there were sunny periods with warmer weather on 3 – 4 December. The temperatures at the Observatory rose to 23.3 degrees on the afternoon of 4 December, the highest of the month. Meanwhile, a replenishment of the northeast monsoon affected Guangdong later on 4 December. Local weather turned mainly cloudy and cooler on 5 December.

Affected by a dry northeast monsoon, apart from cloudier weather on 11 December, it was mainly fine and dry on 6 – 12 December. Under the influence of the replenishment of the northeast monsoon and a broad band of rain-bearing clouds, the weather of Hong Kong became cloudy with a few rain patches on 13 – 16 December. It was also cold on 14 – 15 December.

An intense winter monsoon reached the coast of Guangdong on the night of 16 December. With winds strengthening from the north and reaching gale force offshore and on high ground, local temperatures fell significantly on 17 December. There were also some rain in that morning. The weather turned fine and very dry with cold mornings on 18 - 19 December. The temperatures at the Observatory dropped to a minimum of 9.4 degrees on the morning of 18 December, the lowest of the month. Dominated by a dry northeast monsoon, local weather remained fine on 20 – 28 December. It was also very dry during the day on 21 – 24 December. With the arrival of the replenishment of the northeast monsoon, the weather turned cloudier with a few light rain patches at first on 29 December, before the returning of fine and dry weather in the afternoon and the last two days of the month. It was also cold on the morning of 31 December.

One tropical cyclone occurred over the South China Sea and the western North Pacific in December 2022

Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.5.  Monthly meteorological figures and departures from normal for December are tabulated in Table 2.

Warnings and Signals issued in December 2022

Table 1.1   Strong Monsoon Signal

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
16 / 12	1620	18 / 12	1440

Table 1.2   Thunderstorm Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
17 / 12	0329	17 / 12	0500

Table 1.3   Fire Danger Warnings

Colour	Beginning Time		Ending Time
	Day/Month	HKT	Day/Month	HKT
Yellow	4 / 12	0600	4 / 12	1800
Yellow	10 / 12	0600	11 / 12	0600
Red	11 / 12	0600	11 / 12	2330
Red	17 / 12	1200	19 / 12	2300
Red	21 / 12	0600	25 / 12	2300
Yellow	26 / 12	0600	26 / 12	2100
Yellow	27 / 12	0600	27 / 12	1845
Red	29 / 12	0615	29 / 12	2300
Yellow	31 / 12	0600	31 / 12	2300

Table 1.4   Frost Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
18 / 12	1630	19 / 12	0745

Table 1.5   Cold Weather Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
13 / 12	1620	15 / 12	1145
16 / 12	1620	20 / 12	0915
31 / 12	0605	31 / 12	1145

Table 2   Figures and Departures from Normal - December 2022

Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	19.0 degrees C	1.4 degrees below normal
Mean Air Temperature	16.6 degrees C	1.6 degrees below normal
Mean Daily Minimum Air Temperature	14.4 degrees C	1.8 degrees below normal
Mean Dew Point Temperature	9.3 degrees C	3.1 degrees below normal
Mean Relative Humidity	64 %	6 % below normal
Mean Cloud Amount	51 %	6 % below normal
Total Rainfall	25.7 mm	3.1 mm below normal
Number of hours of Reduced VisibilityΔ	18 hours	170.5 hours below normal§
Total Bright Sunshine Duration	188.5 hours	26.9 hours above normal
Mean Daily Global Solar Radiation	12.89 Megajoule / square metre	1.98 Megajoule above normal
Total Evaporation	80.6 mm	0.3 mm below 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 2021

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