THE ENVIRONMENT
and expertise gained from these projects will enable the laboratory to furnish policy- makers with top-quality information.
Climate
Hong Kong's climate is sub-tropical, tending towards the temperate for nearly half the year. During November and December, there are pleasant breezes, plenty of sunshine and comfortable temperatures. Many people regard these as the best months of the year. January and February are cloudier, with occasional cold fronts followed by dry northerly winds. Temperatures can drop below 10°C in urban areas but sub- zero temperatures and frost occur only at times on high ground and in the New Territories.
March and April can be very pleasant with occasional spells of high humidity. Fog and drizzle can sometimes disrupt air traffic and ferry services because of reduced visibility.
May to August are hot and humid with occasional showers and thunderstorms, particularly during the mornings. Afternoon temperatures often exceed 31°C, but at night temperatures generally remain around 26°C.
Hong Kong is most likely to be affected by typhoons in September, although tropical cyclones of varying strength are not unusual at any time between May and November. On average, about 31 tropical cyclones form over the western North Pacific and the China Seas every year, and about half of them reach typhoon strength with maximum winds of 118 kilometres per hour or more.
When a tropical cyclone is about 700 to 1 000 kilometres southeast of Hong Kong, the weather is usually fine and exceptionally hot, but isolated thunderstorms sometimes occur in the evenings. If the cyclone's centre comes closer to the territory, winds will increase and rain can become heavy and widespread. The heavy rain may last for a few days, and subsequent landslips and flooding sometimes cause considerably more damage than the winds.
The mean annual rainfall ranges from around 1 300 millimetres at Waglan Island to more than 3 000 millimetres around Tai Mo Shan. About 80 per cent of the rain falls between May and September. August is the wettest month, when it rains about four days out of seven with a monthly average at the Royal Observatory of 391.4 millimetres. The driest month is January with 23.4 millimetres and rain falls only about six days in the month.
Severe weather phenomena that can affect Hong Kong include tropical cyclones, strong winter and summer monsoon winds, monsoon troughs and thunderstorms with associated squalls that are most frequent from April to September. Waterspouts and hailstorms occur infrequently, while snow and tornadoes are rare. Climatological data are given in Appendix 50.
The Year's Weather
Eight tropical cyclones necessitated the hoisting of local Tropical Cyclone Warning Signals in 1995, compared with the annual average figure of about six, and the No. 8 Gale or Storm Signal was hoisted three times. The first half of the year was particularly dry with rainfall amounting to only 427.6 millimetres, 57 per cent below the normal of 992.5 millimetres for the same period and the fourth-lowest on record. However, heavy rainfall in July and August associated with active southwest
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