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The Weather of June 2015

3 July 2015

    June 2015 was the hottest June in Hong Kong since records began in 1884.  The monthly mean temperature of 29.7 degrees was 1.8 degrees above the normal figure of 27.9 degrees and broke the previous record of 29.0 degrees set in 2014 by a wide margin of 0.7 degree.  Both the monthly mean minimum temperature of 27.7 degrees and the monthly mean maximum temperature of 32.3 degrees ranked the highest for June.  The extremely hot weather in June 2015 in Hong Kong was partly attributed to the westward extension of the subtropical ridge of high pressure from the western North Pacific to southern China during the month.  The prevailing southerly flow and the above-normal sea surface temperature over the northern part of the South China Sea also contributed to the sweltering weather.

    Under the dominance of the subtropical ridge, the month was also sunnier and drier than usual.  The total duration of sunshine in June 2015 was 192.8 hours, 46.7 hours above the normal figure of 146.1 hours.  The total rainfall of the month was 302.1 millimetres, about 34 percent below the normal figure of 456.1 millimetres.  The accumulated rainfall since 1 January of 981.7 millimetres was about 11 percent below the normal figure of 1096.9 millimetres for the same period.

    Under the influence of a trough of low pressure, the weather in Hong Kong was cloudy with a few showers and thunderstorms on the first day of the month.  With the subtropical ridge extending westward towards the northern part of the South China Sea, local weather improved with sunny periods on 2 June and became generally fine and hot on 3-4 June.

    Another trough of low pressure brought the clouds and showers back to Hong Kong on 5 and 6 June.  Under the influence of the southwest monsoon, a mixture of sunshine and showers persisted till 11 June.

    As a trough of low pressure reached the south China coast on 12 June, heavy showers and squally thunderstorms affected Hong Kong that morning, with more than 100 millimetres of rain falling over the urban areas.  The southwest monsoon continued to bring hot and showery weather to the territory over the next three days.

    With showery activities easing off, Hong Kong experienced a spell of generally fine and very hot weather from 16 to 20 June.  Daily maximum temperatures on 18 and 19 June soared to 34.2 degrees, the highest of the month.  The sizzling hot conditions persisted into 20 June with a maximum temperature of 34.1 degrees that day making it the hottest Tuen Ng Festival on record.

    Meanwhile, a low pressure area over the central part of the South China Sea developed into a tropical depression on 20 June.  It moved generally northward towards Hainan Island and intensified into a tropical storm named Kujira the next day.    Kujira made landfall over the east coast of Hainan Island on the evening of 22 June and moved across Beibu Wan over the next couple of days.  The outer rainbands of Kujira brought scattered showers and squally thunderstorms to Hong Kong from 21 to 25 June.

    With the remnant rainbands of Kujira dissipating, showers eased off on 26 June, and the weather became sunny and very hot in Hong Kong towards the end of the month.

Long Term Trend of Monthly Mean Temperature for June recorded at the Hong Kong Observatory (1884–2015)
Long Term Trend of Monthly Mean Temperature for June recorded at the Hong Kong Observatory (1884–2015)


Years with the hottest June on record in Hong Kong (1884–2015)

Years with the hottest June on record in Hong Kong (1884–2015)

   Two tropical cyclones occurred over the South China Sea and the western North Pacific in the month.

    Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.4.  Monthly meteorological figures and departures from normal for June are tabulated in Table 2.


 

Warnings and Signals issued in June 2015


Table 1.1   Tropical Cyclone Warning Signals

Name of
Tropical Cyclone		 Signal
Number		 Beginning Time Ending Time
Day/Month HKT Day/Month HKT
KUJIRA 1 21 / 6 2140 23 / 6 0740


Table 1.2   Rainstorm Warning Signals

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 12 / 6 0300 12 / 6 0420


Table 1.3   Thunderstorm Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 6 0405 1 / 6 0645
1 / 6 1145 1 / 6 1400
2 / 6 0310 2 / 6 0400
2 / 6 1940 2 / 6 2045
3 / 6 1128 3 / 6 1230
5 / 6 1250 5 / 6 1500
5 / 6 1935 5 / 6 2200
6 / 6 1225 6 / 6 1325
10 / 6 1125 10 / 6 1530
11 / 6 0547 11 / 6 0630
11 / 6 2210 12 / 6 0530
12 / 6 1150 12 / 6 1430
14 / 6 0820 14 / 6 1130
14 / 6 2110 14 / 6 2215
15 / 6 0705 15 / 6 0845
21 / 6 1400 22 / 6 0730
22 / 6 0840 22 / 6 1300
22 / 6 1500 22 / 6 1715
22 / 6 2318 23 / 6 1130
23 / 6 1330 23 / 6 1500
23 / 6 1955 23 / 6 2130
24 / 6 0335 24 / 6 1000
25 / 6 0130 25 / 6 1330
26 / 6 0733 26 / 6 0845


Table 1.4   Very Hot Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
3 / 6 0945 4 / 6 1800
7 / 6 0945 7 / 6 1800
14 / 6 1145 14 / 6 1700
15 / 6 1245 20 / 6 1800
27 / 6 0745 5 / 7 1900


Table 2   Figures and Departures from Normal - June 2015

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 32.3 degrees C 2.1 degrees above normal
Mean Air Temperature 29.7 degrees C 1.8 degrees above normal
Mean Daily Minimum Air Temperature 27.7 degrees C 1.5 degrees above normal
Mean Dew Point Temperature 25.7 degrees C 1.1 degrees above normal
Mean Relative Humidity 80 % 2 % below normal
Mean Cloud Amount 69 % 8 % below normal
Total Rainfall 302.1 mm 154.0 mm below normal
Number of hours of Reduced VisibilityΔ 0 hour 19.5 hours below normal§
Total Bright Sunshine Duration 192.8 hours 46.7 hours above normal
Mean Daily Global Solar Radiation 18.88 Megajoule / square metre 4.69 Megajoule above normal
Total Evaporation 141.7& mm 24.6 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 1981 - 2010 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2014

  &   Data incomplete

daily values of selected meteorological elements for HK for June 2015

The percentile map of mean temperature of June 2015

  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 1981 to 2010



Rainfall Map For June 2015 (isohyets are in millimetres)

Extract of Meteorological Observations in Hong Kong for June 2015