Monthly Meteorological Normals for Hong Kong

Table 1. Monthly mean numbers of days with tropical cyclone warning signals and Strong Monsoon Signal in Hong Kong between 1981-2010

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	-	-	-	-	4.00
February	-	-	-	-	4.63
March	-	-	-	-	4.43
April	0.20	0.13	-	-	2.90
May	0.40	0.23	0.07	-	1.53
June	1.80	0.93	0.20	0.03	1.27
July	3.33	1.73	0.57	0.03	0.70
August	3.83	1.50	0.57	0.10	0.27
September	3.83	1.87	0.53	0.10	1.97
October	2.00	1.03	0.07	-	4.13
November	0.40	0.07	-	-	4.77
December	-	-	-	-	4.97
Year	15.80	7.50	2.00	0.27	35.57

Figure 1.1. Monthly mean number of days with tropical cyclone warning signals in Hong Kong between 1981-2010

Figure 1.2. Monthly mean number of days with Strong Monsoon Signal in Hong Kong between 1981-2010

Table 2. Monthly mean of rainfall in Hong Kong between 1981-2010

Month	Total (mm)	Duration (hours)	Number of Days with
			0.1 mm or more	25 mm or more	50 mm or more
January	24.7	46	5.37	0.23	0.00
February	54.4	89	9.07	0.53	0.10
March	82.2	101	10.90	0.87	0.37
April	174.7	99	12.00	2.23	1.10
May	304.7	106	14.67	3.97	1.73
June	456.1	111	19.07	5.27	2.60
July	376.5	85	17.60	4.60	2.27
August	432.2	97	16.93	5.37	2.47
September	327.6	78	14.67	3.80	2.00
October	100.9	46	7.43	1.20	0.70
November	37.6	38	5.47	0.43	0.13
December	26.8	40	4.47	0.20	0.07
Year	2398.5	935	137.63	28.70	13.53

Figure 2. Monthly mean of rainfall in Hong Kong between 1981-2010

Table 3. Monthly mean numbers of days with lightning,thunderstorm and fog reported at the Observatory between 1981-2010

Month	Number of Days with Lightning	Number of Days with Thunderstorm	Number of Days with Fog (Visibility < 1000 m)
January	0.13	0.13	0.30
February	0.90	0.87	1.20
March	1.90	1.77	2.00
April	4.13	3.50	1.03
May	6.77	5.20	0.07
June	9.07	7.03	-
July	9.77	6.60	-
August	11.23	8.33	-
September	7.13	4.40	-
October	0.97	0.53	-
November	0.27	0.23	-
December	0.03	-	0.03
Year	52.30	38.60	4.63

Table 4. Monthly means of daily maximum, mean and minimum temperature recorded at the Observatory between 1981-2010

Month	Mean Daily Maximum (deg. C)	Mean (deg. C)	Mean Daily Minimum (deg. C)
January	18.6	16.3	14.5
February	18.9	16.8	15.0
March	21.4	19.1	17.2
April	25.0	22.6	20.8
May	28.4	25.9	24.1
June	30.2	27.9	26.2
July	31.4	28.8	26.8
August	31.1	28.6	26.6
September	30.1	27.7	25.8
October	27.8	25.5	23.7
November	24.1	21.8	19.8
December	20.2	17.9	15.9
Year	25.6	23.3	21.4

Figure 4. Monthly means of daily maximum, mean and minimum temperature recorded at the Observatory between 1981-2010

Table 5. Monthly means of relative humidity, dew point temperature, wet-bulb temperature and vapour pressure recorded at the Observatory between 1981-2010

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	66	11.4	13.8	14.0
February	80	83	73	13.0	14.7	15.5
March	82	85	75	15.7	17.2	18.4
April	83	87	77	19.4	20.6	23.0
May	83	87	76	22.6	23.7	27.7
June	82	86	77	24.6	25.6	31.0
July	81	85	74	25.1	26.1	31.8
August	81	85	74	25.0	26.0	31.7
September	78	83	72	23.4	24.8	29.0
October	73	78	66	20.2	22.1	24.1
November	71	76	63	16.0	18.4	18.8
December	69	74	61	11.9	14.8	14.6
Year	78	82	71	19.0	20.6	23.3

Figure 5.1. Monthly mean of relative humidity recorded at the Observatory between 1981-2010

Figure 5.2. Monthly means of dew point temperature, web-bulb temperature and vapour pressure recorded at the Observatory between 1981-2010

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 1981-2010

Month	Cloud Amount (%)	Bright Sunshine		Daily Global Solar Radiation (MJ/m2)
		Duration (hours)	Percentage of Possible
January	61	143.0	42	10.17
February	74	94.2	29	9.39
March	79	90.8	24	9.96
April	81	101.7	27	11.60
May	76	140.4	34	14.19
June	77	146.1	36	14.19
July	69	212.0	51	17.17
August	69	188.9	47	15.63
September	66	172.3	47	14.61
October	58	193.9	54	14.05
November	54	180.1	54	12.28
December	52	172.2	51	10.89
Year	68	1835.6	42	12.85

Figure 6.1. Monthly mean of cloud amount recorded at the Observatory between 1981-2010

Figure 6.2. Monthly mean of sunshine duration recorded at King's Park between 1981-2010

Figure 6.3. Monthly mean of daily global solar radiation recorded at King's Park between 1981-2010

Table 7. Monthly means of prevailing wind direction and mean wind speed recorded at the Observatory and Waglan Island between
1981-2010

Month	Observatory		Waglan Island
	Prevailing Wind Direction (deg.)	Mean Wind Speed (km/h)	Prevailing Wind Direction (deg.)	Mean Wind Speed (km/h)
January	090	10.6	060	25.3
February	090	11.7	070	24.5
March	090	12.0	060	23.0
April	090	11.5	070	20.9
May	090	10.7	080	19.7
June	090	10.6	220	22.9
July	260	10.7	230	21.3
August	090	10.2	230	19.4
September	090	11.4	090	22.6
October	090	12.1	080	27.4
November	090	11.0	080	27.0
December	090	10.0	070	26.0
Year	090	11.0	080	23.3

Figure 7. Monthly means of prevailing wind direction and mean wind speed recorded at the Observatory and Waglan Island between 1981-2010

Table 8. Monthly mean of atmospheric pressure recorded at the Observatory between 1981-2010

Month	Mean (hPa)	Mean Diurnal Range (hPa)
January	1020.3	4.1
February	1018.5	4.2
March	1016.0	4.3
April	1012.9	3.9
May	1009.3	3.5
June	1006.1	3.2
July	1005.7	3.4
August	1005.2	3.5
September	1008.9	3.6
October	1014.1	3.6
November	1017.7	3.9
December	1020.5	4.1
Year	1012.9	3.8

Figure8. Monthly mean of atmospheric pressure recorded at the Observatory between 1981-2010

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 1981-2010

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	17.4	17.7	17.6	17.7	71.3	61.2
February	16.8	17.1	16.8	16.9	59.9	58.7
March	18.0	18.3	18.0	18.2	70.5	65.3
April	21.0	21.4	20.9	21.1	83.8	81.6
May	24.5	25.0	24.6	24.8	110.7	101.8
June	26.5	26.9	26.5	26.7	117.1	108.0
July	26.6	27.1	26.9	27.2	146.2	125.9
August	26.6	27.1	27.1	27.3	134.9	120.6
September	27.1	27.5	27.4	27.7	125.9	100.3
October	26.3	26.6	26.4	26.6	123.9	96.0
November	23.4	23.7	23.3	23.5	99.5	78.8
December	19.8	20.1	19.8	20.0	83.7	64.1
Year	22.8	23.2	22.9	23.2	1227.3	1062.4

Figure9.1. Monthly means of sea surface temperature recorded at North Point and Waglan Island between 1981-2010

Figure9.2. Monthly means of evaporation and potential evapotranspiration recorded at King's Park between 1981-2010

Table 10. Monthly mean of soil temperature recorded at the Observatory between 1981-2010

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	18.8	18.7	20.3	20.3	21.5	21.5
February	19.0	18.9	19.9	19.9	20.7	20.7
March	20.9	20.9	21.0	21.0	21.3	21.3
April	23.5	23.5	22.9	23.0	22.6	22.7
May	26.6	26.6	25.6	25.7	24.8	24.9
June	28.5	28.5	27.6	27.7	26.9	26.9
July	29.8	29.8	29.0	29.0	28.2	28.3
August	30.0	29.9	29.4	29.4	28.9	28.9
September	29.6	29.5	29.3	29.3	29.1	29.0
October	27.8	27.7	28.1	28.1	28.2	28.2
November	24.5	24.4	25.7	25.6	26.4	26.4
December	21.0	21.0	22.8	22.8	24.1	24.1
Year	25.0	25.0	25.1	25.2	25.2	25.2