Monthly Meteorological Normals for Hong Kong (1991-2020)

Table 1. Monthly mean numbers of days with tropical cyclone warning signals and Strong Monsoon Signal in Hong Kong between 1991-2020

Month	Number of Days with Tropical Cyclone Warning Signal				Number of Days with Strong Monsoon Signal
	No. 1 and/or higher	No. 3 and/or higher	No. 8 and/or higher	No. 9 and/or No. 10
January	-	-	-	-	3.63
February	-	-	-	-	3.90
March	-	-	-	-	4.93
April	0.20	0.13	-	-	2.37
May	0.27	0.13	0.03	-	1.50
June	2.00	1.00	0.27	0.03	0.90
July	3.13	1.53	0.53	0.10	0.90
August	4.17	1.90	0.80	0.17	0.37
September	3.83	1.87	0.67	0.10	2.03
October	1.70	0.73	0.13	-	4.10
November	0.57	0.13	-	-	4.30
December	-	-	-	-	5.13
Year	15.87	7.43	2.43	0.40	34.07

Figure 1.1. Monthly mean number of days with tropical cyclone warning signals in Hong Kong between 1991-2020

Figure 1.2. Monthly mean number of days with Strong Monsoon Signal in Hong Kong between 1991-2020

Table 2. Monthly mean of rainfall in Hong Kong between 1991-2020

Month	Total (mm)	Duration (hours)	Number of Days with
			0.1 mm or more	25 mm or more	50 mm or more
January	33.2	55	5.70	0.43	0.00
February	38.9	87	7.97	0.33	0.07
March	75.3	108	10.50	0.77	0.30
April	153.0	98	11.37	1.87	0.87
May	290.6	112	15.37	3.93	1.63
June	491.5	118	19.33	6.03	2.90
July	385.8	93	18.43	4.83	2.10
August	453.2	103	17.50	5.83	2.63
September	321.4	77	14.90	3.77	1.97
October	120.3	50	7.83	1.33	0.77
November	39.3	45	5.70	0.40	0.13
December	28.8	48	5.30	0.17	0.03
Year	2431.2	993	139.90	29.70	13.40

Figure 2. Monthly mean of rainfall in Hong Kong between 1991-2020

Table 3. Monthly mean numbers of days with lightning,thunderstorm and fog reported at the Observatory between 1991-2020

Month	Number of Days with Lightning	Number of Days with Thunderstorm	Number of Days with Fog (Visibility < 1000 m)
January	0.23	0.23	0.20
February	0.60	0.60	1.10
March	1.53	1.37	1.47
April	3.77	3.13	0.83
May	7.70	5.87	0.07
June	10.70	8.13	-
July	10.80	7.97	-
August	11.53	8.90	-
September	7.07	5.07	-
October	1.17	0.83	-
November	0.23	0.17	-
December	0.03	-	0.03
Year	55.37	42.27	3.70

Figure 3. Monthly mean numbers of days with lightning, thunderstorm and fog reported at the Observatory between 1991-2020

Table 4. Monthly means of daily maximum, mean and minimum temperature recorded at the Observatory between 1991-2020

Month	Mean Daily Maximum (deg. C)	Mean (deg. C)	Mean Daily Minimum (deg. C)
January	18.7	16.5	14.6
February	19.4	17.1	15.3
March	21.9	19.5	17.6
April	25.6	23.0	21.1
May	28.8	26.3	24.5
June	30.7	28.3	26.5
July	31.6	28.9	26.9
August	31.3	28.7	26.7
September	30.5	27.9	26.1
October	28.1	25.7	23.9
November	24.5	22.2	20.3
December	20.4	18.2	16.2
Year	26.0	23.5	21.6

Figure 4. Monthly means of daily maximum, mean and minimum temperature recorded at the Observatory between 1991-2020

Table 5. Monthly means of relative humidity, dew point temperature, wet-bulb temperature and vapour pressure recorded at the Observatory between 1991-2020

Month	Relative Humidity (%)			Dew Point Temperature (deg. C)	Wet-bulb Temperature (deg. C)	Vapour Pressure (hPa)
	Mean	Mean at 0200 hours	Mean at 1400 hours
January	74	78	67	11.7	14.0	14.2
February	79	83	72	13.2	15.0	15.7
March	82	86	75	16.1	17.5	18.7
April	83	87	75	19.7	20.9	23.4
May	83	87	76	23.0	24.0	28.2
June	82	86	76	24.9	25.9	31.6
July	81	85	74	25.2	26.3	32.1
August	81	86	74	25.1	26.1	31.8
September	78	82	71	23.6	25.0	29.4
October	73	77	65	20.2	22.2	24.1
November	72	77	65	16.7	19.0	19.6
December	70	75	63	12.4	15.1	15.0
Year	78	82	71	19.3	20.9	23.7

Figure 5.1. Monthly mean of relative humidity recorded at the Observatory between 1991-2020

Figure 5.2. Monthly means of dew point temperature, web-bulb temperature and vapour pressure recorded at the Observatory between 1991-2020

Table 6. Monthly means of cloud amount observed at the Observatory and sunshine duration and daily global solar radiation recorded at King's Park between 1991-2020

Month	Cloud Amount (%)	Bright Sunshine		Daily Global Solar Radiation (MJ/m2)
		Duration (hours)	Percentage of Possible
January	62	145.8	43	10.55
February	72	101.7	32	10.24
March	77	100.0	27	10.71
April	77	113.2	30	12.52
May	76	138.8	34	14.46
June	77	144.3	36	14.61
July	72	197.3	48	17.22
August	70	182.1	46	15.73
September	66	174.4	47	14.99
October	58	197.8	55	14.52
November	58	172.3	52	12.26
December	57	161.6	48	10.91
Year	68	1829.3	41	13.23

Figure 6.1. Monthly mean of cloud amount recorded at the Observatory between 1991-2020

Figure 6.2. Monthly mean of sunshine duration recorded at King's Park between 1991-2020

Figure 6.3. Monthly mean of daily global solar radiation recorded at King's Park between 1991-2020

Table 7. Monthly means of prevailing wind direction and mean wind speed recorded at the Observatory and Waglan Island between
1991-2020

Month	Observatory		Waglan Island
	Prevailing Wind Direction (deg.)	Mean Wind Speed (km/h)	Prevailing Wind Direction (deg.)	Mean Wind Speed (km/h)
January	090	9.4	60	25.1
February	090	10.7	60	24.2
March	090	11.1	60	23.0
April	090	9.7	70	20.5
May	090	9.3	80	19.8
June	260	9.2	220	21.6
July	260	9.9	230	21.3
August	260	9.1	230	18.8
September	090	10.1	80	21.4
October	090	10.6	80	26.3
November	090	9.9	70	26.6
December	090	9.2	10	26.4
Year	090	9.9	70	22.9

Figure 7. Monthly means of prevailing wind direction and mean wind speed recorded at the Observatory and Waglan Island between 1991-2020

Table 8. Monthly mean of atmospheric pressure recorded at the Observatory between 1991-2020

Month	Mean (hPa)	Mean Diurnal Range (hPa)
January	1020.1	4.5
February	1018.7	4.5
March	1016.1	4.7
April	1013.0	4.3
May	1009.3	3.8
June	1006.1	3.5
July	1005.6	3.7
August	1005.2	4.0
September	1008.8	3.9
October	1014.0	3.9
November	1017.3	4.2
December	1020.1	4.4
Year	1012.9	4.1

Figure8. Monthly mean of atmospheric pressure recorded at the Observatory between 1991-2020

Table 9. Monthly means of sea surface temperature recorded at North Point and Waglan Island, and evaporation and potential evapotranspiration recorded at King's Park between 1991-2020

Month	Sea Surface Temperature (deg. C)				Evaporation (mm)	Potential Evapotranspiration (mm)
	North Point		Waglan Island
	0700 hours	1400 hours	0700 or 1100 hours	1400 or 1700 hours
January	17.6	17.9	17.7	17.9	69.1	59.2
February	17.0	17.3	17.0	17.2	60.4	54.7
March	18.3	18.7	18.4	18.6	73.2	66.3
April	21.4	21.8	21.3	21.7	87.2	80.3
May	24.7	25.2	24.7	25.2	109.8	95.4
June	26.6	27.0	26.6	27.0	113.8	96.5
July	26.5	27.0	26.5	27.0	142.0	113.8
August	26.6	27.0	26.8	27.2	129.7	108.6
September	27.0	27.4	27.3	27.6	122.8	94.8
October	26.5	26.7	26.6	26.9	122.6	93.0
November	23.7	24.0	23.6	23.9	95.1	78.5
December	20.0	20.3	20.1	20.3	80.9	63.4
Year	23.0	23.3	23.1	23.4	1204.1	1010.8

Figure9.1. Monthly means of sea surface temperature recorded at North Point and Waglan Island between 1991-2020

Figure9.2. Monthly means of evaporation and potential evapotranspiration recorded at King's Park between 1991-2020

Table 10. Monthly mean of soil temperature recorded at the Observatory between 1991-2020

Month	0.5 m		1.0 m		1.5 m
	0700 hours (deg. C)	1900 hours (deg. C)	0700 hours (deg. C)	1900 hours (deg. C)	0700 hours (deg. C)	1900 hours (deg. C)
January	19.1	19.0	20.7	20.7	22.0	22.0
February	19.2	19.2	20.2	20.2	21.1	21.1
March	21.3	21.3	21.5	21.5	21.7	21.7
April	23.9	23.9	23.4	23.4	23.0	23.0
May	26.8	26.8	25.9	25.9	25.0	25.1
June	28.7	28.7	27.9	28.0	27.1	27.1
July	29.8	29.7	29.1	29.1	28.3	28.3
August	29.8	29.8	29.4	29.4	28.9	28.9
September	29.5	29.4	29.4	29.3	29.0	29.0
October	27.7	27.6	28.2	28.2	28.2	28.2
November	24.8	24.7	26.0	25.9	26.6	26.6
December	21.6	21.6	23.5	23.4	24.6	24.6
Year	25.2	25.1	25.4	25.4	25.5	25.5