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April 2010 was cooler and gloomier than usual. Frequent passage of cold fronts brought the monthly temperature to 21.0 degrees, about 1.5 degrees below normal. The total bright sunshine duration was 49.2 hours, only 48 percent of the normal figure of 101.8 hours. The month was also drier than usual. The total rainfall in the month was 78.9 millimetres, about 58 percent below the normal figure of 188.5 millimetres. The accumulated rainfall since 1 January was 234.1 millimetres, about 31 percent below the normal figure of 337.1 millimetres for the same period.
Under the influence of a maritime airstream, it was mainly cloudy with coastal fog in Hong Kong on the first day of the month. With the passage of a cold front the next morning, the weather became cooler with some rain patches between 2 and 4 April. The return of the maritime airstream brought foggy weather and a few light rain patches to the territory for the ensuing two days. The visibility at Waglan Island fell to around 100 metres during the morning of 5 April.
Another cold front formed over southern China crossed the coast of Guangdong on the morning of 7 April. The northeast monsoon behind the cold front brought cooler weather and some rain to Hong Kong from 7 to 10 April with a few squally thunderstorms on the morning of 8 April. Dominated by a southerly airstream, the weather was warm and foggy from 11 to 13 April. The temperature recorded at the Hong Kong Observatory rose to a maximum of 29.5 degrees during the afternoon of 13 April, the highest of the month.
Meanwhile, a cold front developed over southern China on 12 April and crossed the costal areas of Guangdong later in the afternoon of 13 April. Affected by the strong northeast monsoon behind the cold front, local weather was cloudy with rain from 14 to 18 April. It was also rather cool on 15 and 16 April with the minimum temperature at the Hong Kong Observatory falling to a minimum of 13.5 degrees on 15 April, the lowest of the month. Foggy weather returned on 19 April and persisted for the ensuing two days when a maritime airstream prevailed over the south China coastal areas.
A cold front from southern China crossed the coastal areas of Guangdong and brought occasional rain and a few squally thunderstorms to the territory on 22 April. Gusts of around 100 kilometres per hour associated with the thunderstorms were recorded at Chek Lap Kok. Affected by a continental airstream, the weather turned dry with some sunny periods for the next three days. Another cold front crossed the coastal areas of Guangdong on 26 April. The associated northeast monsoon brought a few rain patches to the territory from 26 to 28 April.
With winds turning light, the visibility at Chek Lap Kok fell to below 1000 metres early on 29 April. A broad rainband developed over western Guangdong and moved eastwards across the Pearl River Estuary, bringing an episode of thundery showers to the territory later in the afternoon of 29 April. Over 50 millimetres of rainfall were recorded over parts of the New Territories and Lantau Island. After the passage of the rainband, there were some sunny periods on the last day of the month.
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