Climate of Hong Kong
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Hong Kong has four seasons: a comfortable to pleasant and dry winter, an unstable and wet spring, a hot and humid summer, and a warm and moderately dry autumn. Hong Kong is affected by both cool northeast monsoons and warm maritime airstreams. Most of the rainfall occurs from May to September, which is the rainy season.
Winter is generally considered the best season to visit Hong Kong, with dry weather, low humidity and comfortable temperatures. In the coldest season, the weather is generally comfortable to warm, with average temperatures hovering between 16.5 °C (61.7 °F) and 23.2 °C (73.8 °F). However, northeast winter monsoons bring frequent cold spells, which can cause the temperature to dip below 10 °C (50 °F) even in urban areas, despite Hong Kong's coastal location just below the Tropic of Cancer. Conversely, it can occasionally get too hot even in Winter; temperatures as high as 28.7 °C (83.7 °F) have been recorded in December. The season starts sunny in December and becomes cloudier towards February. The lowest temperature ever recorded was 0.0 °C (32.0 °F) in 1893, and subzero temperatures have been recorded in the northern New Territories and on high ground. Warm maritime airstreams also commonly raise the temperature above 20 °C (68 °F). The coldest months (February and January) are comfortable to warm with temperatures ranging from about 16.5 °C (61.7 °F) to 22.9 °C (73.2 °F).
Spring brings warmer and more humid weather. It is cooler than autumn, but it is the most humid time of the year. There is a sharp increase in rainfall around April. Temperatures are also noticeably rising with an average temperature of 21.4 °C (70.5 °F) in March to about 28.4 °C (83.1 °F) degrees in May, from warm to hot. Spring weather is very unstable; it could be hot on one day, and cold on the next. The average minimum temperature of the whole season is 19.5 °C (67.1 °F). March starts off as warm as December, but gradually gets hotter towards the end of the month. The average temperature range is usually from 17.2 °C (63.0 °F) to 21.4 °C (70.5 °F), but there are significant temperature variations throughout the month, ranging from below 10 °C (50 °F) to above 25 °C (77 °F) at times. April is warm to hot with temperatures ranging from about 20.8 °C (69.4 °F) to 25 °C (77 °F). The average rainfall is 174.7 millimetres (6.88 in), 92.5 millimetres (3.64 in) more than March. May is warm to hot with average temperatures ranging from about 24.1 °C (75.4 °F) to 28.9 °C (84.0 °F). Spring is the cloudiest time of the year, with March averaging only 90.8 hours of bright sunshine.
Summer weather is hot, humid and unstable. Thunderstorms and brief showers are common, as well as sunny conditions. June has the highest average rainfall of any month. Temperatures are usually above 30 °C (86 °F) during the day, which, coupled with a high humidity (often up to 82% in June), can result in an extreme heat index. Extreme heat indices are also caused by continuous sunshine and low breeze, usually lasting for a long time around July and August, as a result of subtropical high pressure areas. This also occurs before typhoons start hitting Hong Kong or nearby regions in the northeast, e.g. Taiwan or Eastern Coast of China; such outbound airstreams bring even hotter weather, in addition to dirtier air. Nights are also hot with an average minimum temperature of 26.5 °C (79.7 °F). Hong Kong is frequently hit by typhoons in summer.
Temperatures are still high in Autumn (19.8 °C (67.6 °F) to 30.1 °C (86.2 °F)) while humidity and rainfall are considerably lower. Moreover, autumn is the sunniest season in Hong Kong, with October averaging 192.9 hours of bright sunshine. There is a big decrease in rainfall around October while temperatures are gradually decreasing from hot to warm, from 27.7 °C (81.9 °F) in September to 21.8 °C (71.2 °F) in November. September is hot with average temperatures ranging from about 25.8 °C (78.4 °F) to 31.1 °C (88.0 °F). It is also slightly drier than August with an average humidity of 78%. October is warm to hot with average temperatures ranging from 22.7 °C (72.9 °F) to 29.8 °C (85.6 °F). November is comfortable-warm with average temperatures ranging from 19.8 °C (67.6 °F) to 24.1 °C (75.4 °F).
|Jan||16.5-22.6 °C (61.7-72.7 °F)|
|Feb||17.0-22.9 °C (62.6-73.2 °F)|
|Mar||19.2-24.4 °C (66.6-72.3 °F)|
|Apr||21.8-27.0 °C (71.2-80.6 °F)|
|May||24.1-28.9 °C (75.4-84.0 °F)|
|June||26.2-32.2 °C (79.2-90.0 °F)|
|July||26.8-32.4 °C (80.2-90.3 °F)|
|Aug||26.8-32.1 °C (80.2-89.8 °F)|
|Sep||25.8-31.1 °C (78.4-88.0 °F)|
|Oct||22.7-29.8 °C (72.9-85.6 °F)|
|Nov||19.8-24.1 °C (67.6-75.4 °F)|
|Dec||16.9-23.2 °C (62.4-73.8 °F)|
|Climate data for Hong Kong (Hong Kong Observatory)|
|Record high °C (°F)||26.9
|Average high °C (°F)||18.6
|Daily mean °C (°F)||16.3
|Average low °C (°F)||14.5
|Record low °C (°F)||0.0
|Average rainfall mm (inches)||24.7
|Avg. rainy days (≥ 0.1 mm)||5.37||9.07||10.90||12.00||14.67||19.07||17.60||16.93||14.67||7.43||5.47||4.47||137.65|
|Avg. relative humidity (%)||74||80||82||83||83||82||81||81||78||73||71||69||78.0|
|Mean monthly sunshine hours||143.0||94.2||90.8||101.7||140.4||146.1||212.0||188.9||172.3||193.9||180.1||172.2||1,835.6|
|Percent possible sunshine||42||29||24||27||34||36||51||47||47||54||54||51||42|
|Source: Hong Kong Observatory (normals 1981–2010, extremes 1884–1939 and 1947–present)|
Annual Climate Summaries 1997-2015
1997: The year 1997 was the wettest year since records began in 1884. Rainfall at the Hong Kong Observatory amounted to 3,343.0 millimetres (131.61 in), 51 per cent above normal and exceeding the previous record set in 1982.
1998: It was the warmest year since records began in 1884. The annual mean temperature was 24.0 °C (75.2 °F), 0.2 °C (0.4 °F) higher than the previous record set in 1966. The annual mean daily minimum temperature of 22.1 °C (71.8 °F) was also the highest on record.
1999: With an annual mean temperature of 23.8 °C (74.8 °F), 1999 was the third warmest year on record. The monthly mean temperatures for all months except May, August and December were above their respective normal figures.
2000: The year 2000 was warmer and wetter than usual. The mean temperature of 23.3 °C (73.9 °F) was the tenth highest on record and the mean minimum temperature of 21.5 °C (70.7 °F) was the sixth highest. The annual total rainfall of 2,752.3 millimetres (108.36 in) was 24 per cent above normal.
2001: The year 2001 was warmer and wetter than usual. The mean temperature of 23.6 °C (74.5 °F) was 0.6 °C (1.1 °F) above normal, ranking the sixth highest on record. The mean minimum temperature of 21.8 °C (71.2 °F) was the second highest on record. The annual total rainfall of 3,091.8 millimetres (121.72 in) also ranked the fourth highest.
2002: The year 2002 was the second warmest year on record. The mean temperature of 23.9 °C (75.0 °F) was 0.9 °C (1.6 °F) above normal.
2003: The year 2003 was the sixth warmest year since records began in 1884. The mean temperature, 23.6 °C (74.5 °F), was 0.6 °C (1.1 °F) above normal.
2004: Globally, the year 2004 was the fourth warmest year since instrumental temperature records began in 1861. In Hong Kong, 2004 was the ninth warmest year on record. The annual mean temperature was 23.4 °C (74.1 °F), 0.4 °C (0.7 °F) above normal.
2005: Locally in Hong Kong, 2005 was the third wettest year on record. The total rainfall of 3,214.5 millimetres (126.56 in) was 45.2 percent above normal.
2006: Globally, the year 2006 is the sixth warmest year on record. In Hong Kong, it was the eighth warmest year since record began in 1884. The annual mean temperature of 23.5 °C (74.3 °F) was 0.5 °C (0.9 °F) higher than normal.
2007: Under the prolonged dominance of the sub-tropical ridge of high pressure, July 2007 was much drier and warmer than usual. The monthly rainfall of just 76.9 millimetres (3.03 in), less than one quarter of the normal figure of 323.5 millimetres (12.74 in), was the lowest on record for July. With abundant sunshine and little rainfall, the monthly mean temperature was 29.6 °C (85.3 °F), the second highest for July. The accumulated rainfall since the beginning of the year was 1,044.9 millimetres (41.14 in), about 21 percent below the normal figure of 1,316 millimetres (51.8 in) for the same period. The accumulated rainfall for the year was 1,706.9 millimetres (67.20 in), about 23 percent below the normal figure of 2,214.3 millimetres (87.18 in) for the same period.
2008: On the morning of 7 June Hong Kong was lashed by a torrential storm, which dumped up to 300 mm (11.8 in) of rain including 145.5 mm (5.73 in) between 8 am and 9 am killing 3 people. The storm also caused delays to traffic and dozens of flights.
2009: The year 2009 was warmer than usual with an annual temperature of 23.5 °C (74.3 °F). The average temperature in February reached a record high of 20.5 °C (68.9 °F), 4.2 °C (7.6 °F) above the climatological normal. Also, prolonged hot weather extended from summer into late September, with altogether 30 days having daily maximum temperatures of 33 °C (91.4 °F) or above, the most since 1963. The Very Hot Weather Warning was in effect for a total of 40 days, the highest number since the warning started operation in 2000. The year 2009 was also drier than usual. The annual rainfall of 2,182.3 mm (85.92 in) was about 8 percent below normal.
2010: Year 2010 started off with three notably warm months with monthly mean temperatures 0.7 °C (1.3 °F) to 1.6 °C (2.9 °F) above normal. This anomaly was mostly offset by the well below normal monthly mean temperatures in April and June, the former due to frequent passage of late season cold fronts and the latter due to overcast and gloomy weather. With insignificant anomalies of monthly mean temperatures in the second half of the year, the annual mean temperature in 2010 ended up at 23.2 °C (73.8 °F), close to the normal figure of 23.1 °C (73.6 °F). During the year, there were 13 very hot days (daily maximum temperature at 33 °C (91.4 °F) degrees or above) and 21 cold days (daily minimum temperature at 12 °C (53.6 °F) degrees or below), 3 days and 2 days more than normal respectively.
2011: The first month of 2011 was the coldest January since 1977. The temperature did not go above 20 °C (68.0 °F), and the daily mean temperature of the month was only 13.7 °C (56.7 °F). The mean temperature of 2011 was 23 °C (73.4 °F); 0.1 °C (0.2 °F) below the normal figure of 23.1 °C (73.6 °F). The year 2011 was also an exceptionally dry year. With well below normal rainfall in the first nine months, the annual rainfall of 1,476.7 mm (58.14 in) was about 38 per cent below normal, the lowest since 1963.
2012: In Hong Kong, 2012 started with significantly colder than normal weather in January and February which was mainly due to the stronger northeast monsoon over southern China usually in the presence of La Nina. However, with La Nina fading out in spring, the below-normal temperature was compensated by the exceptionally warm weather in April, May and August. Overall, the average temperature of 2012 was 23.4 °C (74.1 °F), 0.3 °C (0.5 °F) above the normal figure of 23.1 °C (73.6 °F).
2013: April 2013 was marked by gloomy and unstable weather which were mainly attributed to the frequent interchange of the cooler northeast monsoon and the humid maritime airstream over the south China coast in the month. The month was more thundery than usual with 8 thunderstorm days, about 4 days more than normal. The sun only shone for 53.6 hours in the month, about 53 percent of the normal total duration of bright sunshine. The total rainfall in the month was 253.8 millimetres (9.99 in), 79.1 millimetres (3.11 in) above the normal amount. The accumulated rainfall for the year as of 30 April was 389.2 millimetres (15.32 in), about 16 percent above the normal figure of 336 millimetres (13.2 in). The annual total rainfall of 2013 was 2,847.3 millimetres (112.10 in), about 19 percent above the normal figure of 2,398.5 millimetres (94.43 in).
2014: With a monthly mean temperature of 29 °C (84.2 °F), June 2014 was the hottest June in Hong Kong since records began in 1884. The monthly mean minimum temperature of 27 °C (80.6 °F) and maximum temperature of 31.5 °C (88.7 °F) were respectively the second and the third highest for June. Such high temperatures were attained despite the facts that sunshine duration and rainfall for the month were not far from normal. The total rainfall of the month was 436.6 millimetres (17.19 in), about 4 percent below the normal figure of 456.1 millimetres (17.96 in). The accumulated rainfall since 1 January up to 31 July of 1,503.4 millimetres (59.19 in) was about 37 percent above the normal figure of 1,096.9 millimetres (43.19 in) for the same period. The annual rainfall of 2014 was 2,638 millimetres (103.9 in), about 10 percent above the normal of 2,398.5 millimetres (94.43 in).
2015: April 2015 was characterized by sunny, warm and relatively dry weather, in particular during the second half of the month. Overall, the total duration of sunshine in April 2015 was 159.2 hours, 57.5 hours above the normal figure of 101.7 hours. The mean temperature of the month was 23.6 degrees, 1.0 degree higher than the normal figure of 22.6 degrees. The monthly mean relative humidity was 77 percent, the third lowest for April since 1961.The monthly rainfall was also less than usual with a deficit of about 63 percent compared to the normal figure of 174.7 millimetres (6.88 in). The accumulated rainfall of 166.6 millimetres (6.56 in) since 1 January up to 30 April was only about one-half of the normal figure of 336.1 millimetres (13.23 in) for the same period. The accumulated rainfall of 679.6 millimetres (26.76 in) since 1 January up to 31 May was about 6 percent above the normal figure of 640.8 millimetres (25.23 in) for the same period. 
- Geography of Hong Kong
- Environment of Hong Kong
- Great Hong Kong Typhoon of 1937
- 1906 Hong Kong typhoon
- "Monthly Meteorological Normals for Hong Kong". Hong Kong Observatory. Retrieved 2012-01-03.
- "Extreme Values and Dates of Occurrence of Extremes of Meteorological Elements between 1884-1939 and 1947-2011 for Hong Kong". Hong Kong Observatory. Retrieved 2012-08-12.
|Wikimedia Commons has media related to Climate of Hong Kong.|
- Hong Kong Observatory web site
- Hong Kong Underground Observatory web site
- The Climate Information site from HKO
- Explanation of Hong Kong's Typhoon Signal System