The Weather of June 2019

Mainly attributing to the warmer than normal sea surface temperature and stronger than usual southerly flow in the lower atmosphere over the northern part of the South China Sea, June 2019 was much hotter than usual in Hong Kong. The monthly mean temperature of 29.0 degrees was 1.1 degree above the normal figure of 27.9 degrees, one of the third highest on record for June. Moreover, the first half of this year from January to June 2019 was exceptionally warm. The mean temperature of 23.0 degrees, mean minimum temperature of 21.3 degrees and mean maximum temperature of 25.4 degrees were all the highest on record for the same period. The monthly rainfall of June 2019 was 429.1 millimetres, about 6 percent below the normal of 456.1 millimetres. The accumulated rainfall recorded in the first six months of the year was 1109.4 millimetres, slightly higher than the normal figure of 1096.9 millimetres for the same period.

Under the influence of a trough of low pressure and an upper-air disturbance, there were heavy showers and squally thunderstorms on the first day of June in Hong Kong. More than 30 millimetres of rainfall were recorded in many places, and rainfall even exceeded 70 millimetres over Sai Kung and Kwun Tong. The upper-air disturbance continued to bring thundery showers to the territory on the next three days. Heavy showers on the morning of 4 June brought more than 90 millimetres of rainfall to Sai Kung District and Eastern District.

With the departure of the upper-air disturbance and strengthening of the anticyclone aloft over the northern part of South China Sea, the weather in Hong Kong turned generally fine and hot apart from isolated showers on 5 – 8 June. With plenty of sunshine, the maximum temperature at the Observatory soared to 33.2 degrees on 7 June, the third hottest Tuen Ng Festival on record. As the anticyclone aloft weakened, local weather became more showery on 9 and 10 June.

Meanwhile, a trough of low pressure over the northern part of south China edged southwards gradually and lingered over the south China coastal areas on 11 – 13 June. Locally, the weather deteriorated again with occasional heavy downpour and squally thunderstorms. More than 160 millimetres of rainfall were recorded at the Observatory in these three days. Under the rain, the temperature at the Observatory dropped to a minimum of 24.6 degrees on 11 June, the lowest of the month. With the trough of low pressure moving away from the coastal areas, local weather turned generally fine during the day on 14 June. Affected by a dry easterly airstream over the coast of Guangdong, the weather in Hong Kong remained generally fine on the next two days. With the weakening of the easterly airstream, it was mainly cloudy with a few showers on 17 – 19 June.

With the anticyclone aloft strengthening again over the south China coast, apart from isolated showers, local weather was fine and very hot during the day on 20 – 23 June. The daily minimum temperature of 29.5 degrees on 21 June was the highest on record for June and the daily mean temperature of 30.8 degrees on the same day was also the hottest Summer Solstice on record. Affected by the trough of low pressure over the south China coast, the weather in Hong Kong became unsettled with outbreaks of heavy showers and thunderstorms on 24 – 26 June. Heavy showers brought more than 80 millimetres of rainfall to Tseung Kwan O, Tai Po and parts of Hong Kong Island in these three days. With the weakening of the trough of low pressure and the prevailing of a southerly airstream, local weather became very hot with a mixture of sunshine and showers towards the end of the month. With plenty of sunshine during the day, the maximum temperature at the Observatory soared to 33.3 degrees on 29 June, the highest of the month. The daily minimum temperature of 29.5 degrees was also recorded on that day, on a par with that of 21 June as the highest on record for June.

One tropical cyclone 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 1.3. Monthly meteorological figures and departures from normal for June are tabulated in Table 2.

Warnings and Signals issued in June 2019

Extract of Meteorological Observations in Hong Kong for June 2019