The Weather of July 2015

    July 2015 was warmer and cloudier than usual. The mean temperature in the month was 29.1 degrees, 0.3 degrees above the normal figure of 28.8 degrees. The monthly mean cloud amount of 75 percent was 6 percent above the normal figure of 69 percent. With the increase in cloudiness, the total sunshine duration recorded in July 2015 was only 164.9 hours, about 22 percent below normal. The month was also wetter than usual with a monthly total rainfall of 406.2 millimetres, 8 percent above the normal figure of 376.5 millimetres. The accumulated rainfall of 1387.9 millimetres since 1 January was about 6 percent below the normal figure of 1473.3 millimetres for the same period.

    The weather in Hong Kong was mainly fine and very hot for the first five days of the month. A weakening trough of low pressure from Guangdong approached the coastal areas, bringing clouds and a few showers to the territory on 6 July. In the mean time, a slow-moving tropical cyclone Linfa hovered over the northeastern part of the South China Sea. Dominated by its circulation, a northerly airstream of continental origin brought mainly fine and relatively dry conditions to the coastal region on 7 and 8 July.

    Meanwhile, Linfa intensified into a typhoon and made landfall over the coast of eastern Guangdong on 9 July. Local winds strengthened gradually in the afternoon with occasional gales on high ground. Tracking generally westwards along the coastal strip of Guangdong, Linfa weakened rapidly during the night. After some morning rain on 10 July, the weather rapidly improved during the day and a spell of very hot weather persisted over the following nine days. The maximum temperature at the Observatory reached 34.4 degrees on 13 July, the highest for the month. However, the weather also became increasingly unsettled with less sunshine and more showers. The showers were thundery at times and heavy in places, particularly over the western part of the territory on 17 July when more than 200 millimetres of rainfall were recorded near Chek Lap Kok in Lantau Island.

    With an area of low pressure lingering over the coast of Guangdong and the development of an embedded trough, the weather deteriorated further on 20 July. Following the dissipation of the trough, rainbands and thunderstorms from the northern part of the South China Sea continued to move in to affect the territory from time to time under the influence of a moist southerly airstream. A waterspout was reported near Kau Yi Chau on the morning of 22 July, and the rain was especially heavy over the urban areas that day and over the northern part of the New Territories on 24 July. Despite the rain easing off and some sunny periods emerging on 27 July, showery conditions continued to affect Hong Kong before the weather turned fine on the last day of the month.