ENG-1964 — Page 284

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GEOGRAPHY AND POPULATION

and is often cloudy and showery with occasional thunderstorms. Summer is the rainy season. The annual rainfall as measured at the Royal Observatory has varied between 35 inches (in 1963) and 120 inches (in 1889) but the mean value is 85 inches. On average the six dry months from October to March yield about 12 inches as compared with 73 inches spread over the six wet months. There is a marked diurnal variation of rainfall in summer with a maximum in the morning, and there are appreciable differences in the rainfall in different parts of the Colony. The wettest areas are the moun- tainous regions particularly around Tai Mo Shan and on Lantau Island.

The mean daily temperature ranges from about 14°C in February to over 28°C in July and the average for the year is 22°C. During the hottest month, July, the mean maximum temperature is 31°C but the summer temperature often exceeds 32°C. February is the coldest month with a mean minimum temperature of 13°C but the temperature can be expected to fall to 7°C in most years. Tem- peratures above 35°C or below 4°C are rarely recorded at the Observatory although greater extremes occur in the New Territories. Ice occasionally forms on high ground. Afternoon temperatures are usually about 5°C higher than those during the coldest part of the night. The mean relative humidity exceeds 80 per cent from mid-February until early September. November is the least humid month with a mean relative humidity of 69 per cent, but the lowest reading of 10 per cent was recorded in January. The average daily duration of bright sunshine ranges from three hours in March to over seven hours in mid-July and late October.

Gales caused by tropical cyclones may be expected in any of the months from May to November but they are most likely from July to September. The passage of these cyclones several times a year at varying distances from Hong Kong brings spells of bad weather with strong winds and heavy rain. Gales are experienced once a year on average, and less frequently the centre of a mature typhoon passes sufficiently close to the Colony to produce winds of hurricane force when damage and loss of life may occur.