Globally, the year 2008 ranked as the 10th warmest year on record. In Hong Kong, the average temperature in 2008 was slightly lower than those for previous years in this century. This was attributable to the La Nina phenomenon at the beginning of the year. The longest cold spell in 40 years occurred from 24 January to 16 February when the minimum temperature stayed below 12 degrees for 24 consecutive days. The year saw other new records. Record-breaking rain fell in April and June 2008, while October 2008 was the warmest October since record began in 1884. The year 2008 was also wetter than usual. The annual rainfall of 3066.2 millimetres was about 29 percent above normal.
In 2008, the typhoon season started in mid-April, the second earliest onset time since 1946. Altogether six tropical cyclones affected Hong Kong and necessitated the issuance of local Tropical Cyclone Warning Signals, which were about normal. Four of them necessitated the issuance of the No. 8 or higher signals, making 2008 the year with the most No. 8 Signals since 1999. Typhoon Nuri crossed Hong Kong in August 2008 and necessitated the issuance of the Increasing Gale or Storm Signal No. 9. This was the first No. 9 signal since the passage of Typhoon Dujuan in September 2003.
January was cloudier and wetter than usual. Cold weather started to affect Hong Kong on 24 January and lasted until 16 February. This exceptionally long cold spell was a result of the cold air from Siberia moving south incessantly to reach central and southern China, while moist air was transported from the South China Sea and from even as far as the Indian Ocean. The convergence between cold and moist air brought continuous cloudy, rainy and cold weather to Hong Kong. The monthly mean temperature of February was 13.3 degrees, the lowest for February in the past 40 years.
March was warmer and sunnier than usual.
April was warmer than usual. The passage of Typhoon Neoguri brought heavy rain to Hong Kong on 19 April, with a rainfall of 237.4 millimetres for the day breaking the April daily figure since record began. The heavy rain necessitated the issuance of the first Black Rainstorm Warning in 2008 which was also the earliest in the year since the start of the Rainstorm Warning System in 1992.
May was cooler and drier than usual.
The weather of June was marked by heavy rain and squally thunderstorms. The hourly rainfall of 145.5 millimetres recorded on 7 June between 8 and 9 a.m. was the highest since record began. The monthly total of 1346.1 millimetres was also a record high among all months since 1884.
July was wetter than usual.
August was sunnier and drier than usual. With long periods of sunshine, the monthly total global solar radiation in August was 564.48 megajoules per square metre, the second highest for August since record began.
September was hotter and drier than usual. The monthly mean temperature of 29.0 degrees equaled the record set in 1969. The passage of Typhoon Hagupit in late September brought storm surges, which combined with high tides led to the highest sea level since Typhoon Wanda in 1962 and brought extensive flooding to many low-lying areas.
October was unseasonably warm. Both the monthly mean temperature of 26.5 degrees and the mean daily minimum temperature of 24.9 degrees broke the records set in 1983 by 0.1 degrees and 0.2 degrees respectively.
November was brighter and warmer than usual.
December was warmer and drier than usual.