326 The Environment
generally range from 0.5 to 1.5 knots, peaking at up to five knots in narrow channels.
Climate
Hong Kong's climate is subtropical, tending towards the temperate for nearly half the year. November and December are generally regarded as the best months of the year with pleasant breezes, plenty of sunshine and comfortable temperatures.
January and February are cloudier, with occasional cold fronts bringing in cold northerly winds. Temperatures can drop below 10 degrees Celsius in urban areas. Sub-zero temperatures and frost occur infrequently on high ground.
March and April can be mild and pleasant but humid. Fog sometimes disrupts air traffic and ferry services because of reduced visibility.
The months from May to August are hot and humid with occasional showers and thunderstorms. Afternoon temperatures often exceed 31 degrees, but at night temperatures generally stay around 26 degrees.
Hong Kong is more likely to be affected by tropical cyclones between June and October. When a tropical cyclone is some 1 000 kilometres southeast of Hong Kong, the weather is usually fine and exceptionally hot. If the centre of the tropical cyclone comes closer to Hong Kong, winds will increase and rain may become heavy and widespread. Landslips and flooding sometimes cause considerably more damage than the winds.
About 80 per cent of the annual rainfall falls between May and September. August is the wettest month and January the driest.
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.
The Year's Weather
Globally, 2004 was the fourth warmest year since instrumental temperature records began in 1861. In Hong Kong, 2004 was the ninth warmest year on record. The annual mean temperature was 23.4 degrees, 0.4 degree above normal. In June, the rain-bearing monsoon trough spent less time near the South China coast, resulting in more sunshine and hence higher temperatures in Hong Kong. This made June 2004 the eighth hottest June on record. The northeast monsoon was also weak during the last two months of the year, giving rise to above-normal temperatures in Hong Kong in these two months.
Three tropical cyclones affected Hong Kong in 2004, about half of the normal figure. Most of the tropical cyclones originating from the western North Pacific moved north or northeast on approaching Luzon and Taiwan and did not enter the South China Sea. They therefore failed to bring the usual rainfall to Hong Kong. The monsoon trough also brought less than normal rainfall to Hong Kong in May and