THE ENVIRONMENT
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winds will increase and rain may become heavy and widespread. The heavy rain may last a few days, and 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 with an average rainfall of 391.4 millimetres at the Hong Kong Observatory and, on average, rain falls on more than half of the days. The driest month is January with only 23.4 millimetres of rain and six rain days on average.
Severe weather phenomena in Hong Kong include tropical cyclones, strong winter and summer monsoon winds, monsoon troughs and thunderstorms with associated squalls. Waterspouts and hailstorms occur infrequently, while snow and tornadoes
are rare.
Climatological data are given in the Appendices.
The Year's Weather
January was warmer and wetter than usual.
February was again warmer but drier than usual.
Warmer and drier weather continued into March. A rainstorm on March 25 necessitated the issuance of the Amber Rainstorm Warning, the earliest rainstorm warning in any year since the revised rainstorm warning system came into effect in 1998.
April was again warmer and drier than usual. Hail fell on April 9 during the passage of thunderstorms.
May was the fourth consecutive month with warmer and drier weather. The accumulated rainfall since January 1 amounted to only 410 millimetres, 33 per cent below the normal figure.
With an active trough of low pressure lingering over the vicinity of the South China coast for about two thirds of the month, the weather in June was marked by persistent heavy rain and thunderstorms. The monthly rainfall amounted to 1 083.6 millimetres, about three times the normal figure. This was also a new record for June, the previous record being 962.9 millimetres in June 1966.
In June, Typhoon Chebi led to the hoisting of the Standby Signal No. 1 in Hong Kong for the first time during the year. Tropical Storm Durian, which developed into a full-fledged typhoon in early July, affected Hong Kong by the end of June and necessitated the hoisting of the Strong Wind Signal No. 3.
July was wetter and cooler than usual. A waterspout formed over the Tathong Channel during the passage of Durian. Typhoon Utor and Typhoon Yutu both necessitated the hoisting of the No. 8 signal in Hong Kong. The last time the No. 8 signal was hoisted twice in July was in 1966.
The weather was warmer and drier than usual in August. The Standby Signal No. 1 was hoisted for Tropical Storm Fitow.
September was warmer and wetter than usual. Typhoon Nari, characterised by its erratic movement and unusually long lifespan of 15 days, necessitated the hoisting of the No. 3 signal in Hong Kong.