With drier northeast monsoon affecting Hong Kong for most of the time and less moisture supply to the coast of southern China in the month, April 2025 was drier than usual in Hong Kong. The monthly mean relative humidity was 74 percent, the second lowest on record for April since 1947. Moreover, the total rainfall in the month was 57.1 millimetres, only about 37 percent of the normal of 153.0 millimetres. The accumulated rainfall recorded in the first four months of the year was 125.5 millimetres, about 42 percent of the normal of 300.4 millimetres for the same period. The month was also sunnier than usual, the monthly total sunshine duration was 155.6 hours, about 37 percent above the normal of 113.2 hours. April 2025 was warmer than usual with a mean temperature of 23.7 degrees, 0.7 degrees above the normal of 23.0 degrees. 

Under the influence of the northeast monsoon and a broad band of clouds covering southern China, the weather was mainly cloudy and cold with one or two light rain patches on the morning of the first day of the month. The temperatures at the Observatory fell to a minimum of 12.9 degrees that morning, the lowest of the month. With the band of clouds thinning out, there were sunny periods during the day. The weather became fine and dry the next day. Under the influence of a dry easterly airstream, it remained fine and very dry on the afternoon of 3 April. While it was generally fine at first on 4 April, a band of clouds gradually covered the coast of Guangdong, leading to cloudier weather that afternoon and the following two days. There were occasional showers on 5 April, with around 10 millimetres of rainfall recorded over many places. With the band of clouds thinning out, the weather became mainly fine on 7 April. It was dry and rather warm during the day. Winds were weak over the coast of Guangdong on 8 – 9 April. The weather in Hong Kong was rather warm with sunny periods. 

A southerly airstream brought humid weather in the following three days. Locally, there were fog patches on the morning of 11 April, with the visibility in the harbour once falling below 1000 metres. Besides, a trough of low pressure over northern Guangdong developed into a cold front on the morning of 12 April. As the cold front edged closer to the coastal region, local showers increased with a few squally thunderstorms that afternoon. More than 10 millimetres of rainfall were recorded over many places, and rainfall even exceeded 20 millimetres over Tai Po District. The cold front moved across the coastal areas around that evening. Under the influence of the associated intense and dry northeast monsoon, showers eased off with temperatures falling gradually that night. Strong northerly winds also affected many parts of Hong Kong that night and at first the next day, with winds occasionally reaching gale force offshore and on high ground. The intense monsoon also transported sand and dust southwards from Mongolia and brought widespread sandstorms to many inland areas in China. Under the influence of the very dry continental airstream and the sand and dust weather, the weather was very dry with visibility slightly dropping to around 5 – 6 kilometres over parts of the territory on 13 – 15 April. The relative humidity over many places on these three days fell below 40 percent. The relative humidity recorded at the Observatory on 13 April once fell to 21 percent, the lowest record in April since the establishment of the automatic weather station at the Observatory's Headquarters in 1984. With plenty of sunshine and weaker winds on 15 April, the temperatures at the Observatory soared to a maximum of 33.0 degrees that afternoon, the highest of the month. It also marked the earliest occurrence of very hot weather in a year and the second highest maximum temperature for April on record.

An easterly airstream affected the coast of Guangdong on 16 – 17 April. While the local weather was mainly fine and dry during the day on 16 April, it became mainly cloudy the next day with coastal fog in the morning and at night. The visibility at Waglan Island once fell below 1000 metres. With a humid southerly airstream replacing the easterly airstream that afternoon, the weather was cloudy with a few showers in the following two days. There was coastal fog on 18 – 21 April. The southerly airstream continued to affect the coast of Guangdong and brought hot weather to Hong Kong on 20 – 24 April. The maximum temperature recorded at the Observatory was 30.6 degrees on 20 April, making it one of the warmest day of Easter on record. 

A trough of low pressure affected inland Guangdong on 24 April and edged closer to the coastal areas in the evening, bringing showers and a few squally thunderstorms that night and the next day. Showers were heavy on the morning of 25 April. More than 30 millimetres of rainfall were recorded over many places, and rainfall even exceeded 50 millimetres over the eastern part of Hong Kong Island, Kwun Tong and Tseung Kwan O. With a fresh to strong easterly airstream setting in that night, the weather was cloudy with a few showers and became cooler in the following two days. There were also fog patches on 27 April. The visibility at Waglan Island once fell below 1000 metres. Another trough of low pressure over inland Guangdong edged closer to the coastal areas gradually that night. Apart from coastal fog on the morning of 28 April, there were showers and one or two thunderstorms that day with rainfall exceeding 10 millimetres over many places, and around 30 millimetres of rainfall were even recorded over the northern part of the New Territories. Affected by a relatively dry easterly airstream, the weather was generally fine on the last two days of the month.

There was no tropical cyclone over the South China Sea and the western North Pacific in April 2025.

Warnings and Signals issued in April 2025

Table 1.1   Strong Monsoon Signal

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
12 / 4	1715	13 / 4	0945

Table 1.2   Rainstorm Warning Signals

Colour	Beginning Time		Ending Time
	Day/Month	HKT	Day/Month	HKT
Amber	25 / 4	0400	25 / 4	0515

Table 1.3   Thunderstorm Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
12 / 4	1427	12 / 4	1900
24 / 4	1850	24 / 4	2130
25 / 4	0137	25 / 4	0700
25 / 4	0727	25 / 4	1540
25 / 4	2318	26 / 4	0115
28 / 4	0705	28 / 4	1110

Table 1.4   Fire Danger Warnings

Colour	Beginning Time		Ending Time
	Day/Month	HKT	Day/Month	HKT
Red	2 / 4	0745	4 / 4	0600
Yellow	4 / 4	0600	4 / 4	1845
Yellow	6 / 4	0600	6 / 4	1530
Red	13 / 4	0600	15 / 4	2330

Table 1.5   Cold Weather Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
29 / 3	2145	1 / 4	0940

Table 1.6   Very Hot Weather Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
15 / 4	1345	15 / 4	1800

Table 2   Figures and Departures from Normal - April 2025

Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	26.7 degrees C	1.1 degrees above normal
Mean Air Temperature	23.7 degrees C	0.7 degrees above normal
Mean Daily Minimum Air Temperature	21.6 degrees C	0.5 degrees above normal
Mean Dew Point Temperature	18.3 degrees C	1.4 degrees below normal
Mean Relative Humidity	74 %	9 % below normal
Mean Cloud Amount	71 %	6 % below normal
Total Rainfall	57.1 mm	95.9 mm below normal
Number of hours of Reduced VisibilityΔ	0 hours	65.9 hours below normal§
Total Bright Sunshine Duration	155.6 hours	42.4 hours above normal
Mean Daily Global Solar Radiation	15.75 Megajoule / square metre	3.23 Megajoule above normal
Total Evaporation	104.3 mm	17.1 mm above normal

Remarks :	All measurements were made at the Hong Kong Observatory except sunshine, solar radiation and evaporation which were recorded at King's Park Meteorological Station and visibility which was observed at the Hong Kong International Airport.
Δ	The visibility readings at the Hong Kong International Airport are based on hourly observations by professional meteorological observers in 2004 and before, and average readings over the 10-minute period before the clock hour of the visibility meter near the middle of the south runway from 2005 onwards. The change of the data source in 2005 is an improvement of the visibility assessment using instrumented observations following the international trend. Before 10 October 2007, the number of hours of reduced visibility at the Hong Kong International Airport in 2005 and thereafter displayed in this web page was based on hourly visibility observations by professional meteorological observers. Since 10 October 2007, the data have been revised using the average visibility readings over the 10-minute period before the clock hour, as recorded by the visibility meter near the middle of the south runway.
*   Departure from 1991 - 2020 climatological normal, except for number of hours of reduced visibility
§   Departure from mean value between 1997 and 2024

Remarks :

Extremely high: above 95th percentile Above normal: between 75th and 95th percentile Normal: between 25th and 75th percentile Below normal: between 5th and 25th percentile Extremely low: below 5th percentile Percentile and 5-day running average values are computed based on the data from 1991 to 2020

Extract of Meteorological Observations in Hong Kong for April 2025