Hong Kong's climate is sub-tropical, 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 on high ground and in the New Territories infrequently.

    March and April can be mild and pleasant but humid. Fog and drizzle sometimes disrupt air traffic and ferry services because of reduced visibility.

    The months from May to August are hot and humid with occasional showers and thunderstorms, particularly in the morning. Afternoon temperatures often exceed 31 degrees, but at night temperatures generally stay around 26 degrees.

    Hong Kong is most likely to be affected by tropical cyclones 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 south-east of Hong Kong, the weather is usually fine and exceptionally hot, but isolated thunderstorms sometimes occur in the evening. If the centre of the tropical cyclone comes closer to Hong Kong, 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 about 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

The year 2002 was the second warmest on record. The mean temperature of 23.9 degrees was 0.9 degree above normal. The first few months of the year was warmer than usual because fewer cold surges had affected Hong Kong. In May and June, the monsoon trough which normally brings a lot of rain to Hong Kong was quite inactive, resulting in more days with sunny weather and hence higher temperatures. While the first half of the year was exceptionally warm, the temperature in the second half of the year was near normal.

    The tropical cyclone season started much later than usual, with the first tropical cyclone warning signal issued on August 3. Only three tropical cyclones affected Hong Kong in 2002, about half the normal figure. All three had originated in the South China Sea. During the year, none of those tropical cyclones originating over the western North Pacific entered the South China Sea to affect Hong Kong. This was due largely to the development of an El Niño, which was characterised by above normal sea surface temperatures in the equatorial eastern and central Pacific. The associated change in atmospheric steering flow caused tropical cyclones over the western North Pacific to turn towards the north before entering the South China Sea.

    January was warmer than normal. It was warmer and sunnier than usual in February. A monthly mean temperature of 21.5 degrees made March the warmest March on record. The monthly total rainfall of 238.7 millimetres was more than three times the normal amount for the month.

    April was warmer, sunnier and drier than usual. It was warmer and slightly drier than normal in May. Warmer weather continued into June with a mean temperature of 28.8 degrees, which ranked the second highest for June. The weather became cloudier than usual in July.

    With the approach of Severe Tropical Storm Kammuri, the first Tropical Cyclone Warning Signal of the year was issued in early August. Kammuri missed Hong Kong and eventually made landfall near Shanwei. In mid-August, Severe Tropical Storm Vongfong moving across the South China Sea to the southwest of Hong Kong led to the issuance of the Standby Signal No. 1. August as a whole was slightly drier than normal.

    It was rainy in September. The monthly rainfall of 723 millimetres was about 2.4 times the normal amount and ranked the fourth highest for the month. The approach of Severe Tropical Storm Hagupit necessitated the issuance of the No. 8 Southeast Gale or Storm Signal in Hong Kong. Hagupit passed about 150 kilometres to the south-southwest of Hong Kong and made landfall near Yangjiang.

    October was cloudier and wetter than usual. Total bright sunshine duration of the month was the second lowest on record. The Red Rainstorm Warning issued on October 18 was the latest such warning ever issued in a year.

    November was drier than usual. The monthly rainfall was 34 per cent below the normal amount. December was cloudier and wetter than usual. On December 19, thunderstorms associated with a cold front affected the New Territories and necessitated the issuance of the Thunderstorm Warning for the first time in December in over 30 years.