The Longest Cold Spell since 1968

Under the influence of the winter monsoon, it was persistently cold in Hong Kong during the past three weeks. Up to today (13 February), the minimum temperatures recorded at the Hong Kong Observatory stay below 12 degrees Celsius for 21 days consecutively. This is the longest cold spell in Hong Kong since 1968. During this period, the mean minimum temperature recorded at the Hong Kong Observatory was 9.9 degrees, the second lowest during the same period (24 January - 13 February) since record began in 1885.

This exceptionally long cold spell was a result of the cold air from Siberia moving south to reach central and southern China incessantly, while moist air was transported from the South China Sea and even as far as the Indian Ocean. The rendezvous of the cold and moist air brought continuous cloudy, rainy and cold weather to the region. Under the dominance of the winter monsoon, winds in Hong Kong were northerly during the entire period from 24 January to 13 February, whereas the normal rate of occurrence of northerly winds is only 63 percent.

Concurrently, sea surface temperatures over the central and eastern tropical Pacific have been persistently cooler than normal since last autumn and a La Ni?a event was established in January this year. Past studies showed that the winter monsoon affecting mainland China would be stronger and more frequent than normal during winter seasons with La Ni?a. In Hong Kong, statistics show that when a La Ni?a occurs during winter seasons, there is a higher chance of normal or below normal temperatures.

In the next few days, the winter monsoon will continue to bring cold weather to south China. Morning temperatures in the urban areas in Hong Kong will hover between 10 - 11 degrees Celsius. It will be brighter with more sunshine on Friday, when the afternoon temperature will reach 15 - 16 degrees. The forecast for the next 7 days is that the morning temperatures in the urban area will be around 12 degrees, i.e. a couple of degrees higher than that of the past 3 weeks.