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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 June 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 in June this year ranked the highest for June. The extremely hot weather 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, June 2015 was sunnier and drier than usual. The total duration of sunshine in the month was 192.8 hours, 46.7 hours above the normal figure of 146.1 hours. The total rainfall of the month was 291.0 millimetres, about 36 per cent below the normal figure of 456.1 millimetres. The accumulated rainfall since January of 970.6 millimetres was about 12 per cent below the normal figure of 1 096.9 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 June 2 and became generally fine and hot on June 3 and 4.
Another trough of low pressure brought the clouds and showers back to Hong Kong on June 5 and 6. Under the influence of the southwest monsoon, a mixture of sunshine and showers persisted until June 11.
As a trough of low pressure reached the south China coast on June 12, heavy showers and squally thunderstorms affected Hong Kong that morning, with more than 100 millimetres of rainfall 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 June 16 to 20. Daily maximum temperatures on June 18 and 19 soared to 34.2 degrees, the highest of the month. The sizzling hot conditions persisted to June 20 with a maximum temperature of 34.1 degrees, 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 June 20. 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 June 22 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 June 21 to 25.
With the remnant rainbands of Kujira dissipating, showers eased off on June 26 and the weather became sunny and very hot in Hong Kong towards the end of the month.
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 summarised in Table 1. Monthly meteorological figures and departures from normal for June are tabulated in Table 2.
Ends/Friday, July 3, 2015
Issued at HKT 18:29
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