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THE ENVIRONMENT
the first half of the month, Hong Kong was under the influence of a warm and moist airstream from the South China Sea and the weather was mainly cloudy and humid with light rain patches and coastal fog. However, drier air from the north affected Hong Kong during the remainder of the month and fire danger warnings were issued twice during this period.
April was also warm and dry. The mean temperature of 24.0°C was highest on record for the month and was equalled only once before, in April 1964. The strong monsoon signal was hoisted three times, twice to warn strong northeast winds and once to warn strong southwesterlies. Thunderstorms were reported on several days and there was a hailstorm over the northwestern part of the New Territories on April 7. Warm and humid air from the southeast caused mist and fog patches over Hong Kong for eight days and resulted in the diversion of 23 aircraft.
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May was wetter and hotter than usual with rainfall more than 75 per cent above average. During the month there were only two days on which no rainfall was re- corded at the Royal Observatory. Cold fronts from the north and troughs over the South China Sea brought heavy rain and widespread thunderstorms and thunder- storm and/or heavy rain warnings were issued on 10 days.
In June, both the rainfall and air temperature were close to average. However, there was no tropical cyclone during the month and the rain was mostly associated with passages of active troughs from the north.
-Six tropical cyclones formed over the western North Pacific and the South China Sea in July. Of these only Typhoon Dot and Tropical Storm Wilda necessitated the hoisting of tropical cyclone warning signals in Hong Kong.
The first tropical cyclone for the year was Tropical Storm Wilda which passed about 200 miles east of Hong Kong on July 3. Typhoon Dot formed in the South China Sea on July 14 and passed about 12 miles to the east of the Royal Observatory early on July 17. Gales and heavy showers were experienced in Hong Kong during the passage of Dot and some flooding was also reported in low-lying areas. This typhoon contributed about one-third of the month's total rainfall which was nearly 90 per cent above average.
During August, seven tropical cyclones formed over the western North Pacific and the South China Sea, but only three, Typhoon Georgia and Tropical Storms Joan and Kate, affected Hong Kong. They all passed within 180 miles to the south and caused periods of strong winds and heavy rain. The rainfall for the month was more than double the average figure and was the second highest on record for August. The total rainfall from May to August and from January to August were both the highest ever recorded. On August 30, the strong monsoon signal was hoisted for four hours to warn strong easterly winds.
The abnormally wet weather of July and August continued during September. The rainfall recorded was more than 70 per cent above average while the accumulated total from January 1 up to the end of September exceeded the rainfall of the previous wettest year, 1889. During the month Typhoon Marge and Severe Tropical Storm