Attributed to the stronger-than-normal upper-air anticyclone over southern China, September 2026 was hotter and drier than usual. The monthly mean minimum temperature of 27.1 degrees was 1.0 degrees above the normal and the fifth highest on record for September. The monthly mean temperature of 28.8 degrees and mean maximum temperature of 31.8 degrees were 0.9 degrees and 1.3 degrees above their respective normals and both were one of the tenth highest on record for September.  Moreover, the monthly mean relative humidity of 74 percent was 4 percentage points below the normal of 78 percent and was one of the sixth lowest on record for September. Rainfall in the month was only 94.3 millimetres, about 29 percent of the normal of 321.4 millimetres. The accumulated rainfall in the first nine months of the year was 2451.9 millimetres, about 9 percent above the normal of 2242.8 millimetres for the same period.

After Saudel re-intensified into a tropical depression on the last day of August, it moved northeastwards across the northern part of the South China Sea on 1 September and skirted about 200 kilometres southeast of Hong Kong. It further intensified into a tropical storm on the next day before making landfall over Zhangzhou, Fujian on the morning of 3 September. It then moved across the eastern part of inland Guangdong and weakened gradually. Locally, under the combined effect of Saudel and the northeast monsoon, there were occasional strong winds offshore and on high ground on 1 September. There were occasional squally showers and thunderstorms. Around 20 millimetres of rainfall were generally recorded over the territory, and rainfall even exceeded 40 millimetres over the eastern part of the New Territories. With the departure of Saudel, showers decreased and there were sunny intervals during the day on 2 – 3 September.

Winds over Hong Kong were weak in the next five days. Apart from isolated showers, local weather became generally fine on 4 – 5 September. However, a band of clouds covered Guangdong on 6 September and brought a few showers to the territory. There were more showers in some areas in the morning. Around 10 millimetres of rainfall were recorded over many places, and rainfall even exceeded 40 millimetres over the northeastern part of the New Territories. Under light wind conditions, daytime heating triggered showers over inland Guangdong the next day. The heat-triggered showers moved southwards and affected the territory that afternoon with more than 20 millimetres of rainfall recorded over Yuen Long and Tsuen Wan Districts. With the thinning out of the cloud bands, the weather of Hong Kong turned mainly fine apart from isolated showers on 8 September.

The northeast monsoon affected southern China in the next four days. Locally, the weather was dry during the day with a mixture of sunny periods and a few showers. Showers were heavier with more than 20 millimetres over North District on the morning of 10 September. Under the showers in the small hours on 11 September, the temperature at the Observatory dropped to a minimum of 25.5 degrees, the lowest of the month. With plenty of sunshine, it was very hot on 12 September. Under the combined effect of a strong northeast monsoon and a tropical depression over the seas to the east of Vietnam, local winds strengthened gradually on 12 September and persisted until the next day. Local weather was mainly cloudy with sunny intervals and a few showers on 13 September.

The northeast monsoon moderated on 14 September and a band of clouds over the coast of Guangdong brought a few showers to the territory. Showers were heavier in some areas with thunderstorms. More than 40 millimetres of rainfall were recorded over parts of the North District, Tuen Mun and Kowloon. Under the influence of a replenishment of the northeast monsoon, local weather was mainly cloudy with a few showers on 15 September and became generally fine on the following two days. It was dry in the afternoon of 17 September. Affected by an anticyclone aloft, local weather remained dry during the day and generally fine on 18 – 20 September. It was very hot on 19 – 20 September.

Winds were weak over the coast of Guangdong on 21 September. Locally, it was still very hot with sunny periods. Upper-air disturbances brought a few showers and thunderstorms to the territory on 22 September. Around 5 millimetres of rainfall were recorded over Hong Kong Island and parts of the New Territories East. Under the influence of the northeast monsoon, the weather of Hong Kong was generally fine apart from isolated showers in the mornings on 23 – 24 September. The northeast monsoon moderated and an anticyclone aloft continued to bring mainly fine weather to the coast of Guangdong on 25 – 30 September. Local weather remained dry during the day and generally fine in the last six days of the month, apart from isolated showers on 28 – 30 September. It was also very hot on 29 – 30 September. With abundant sunshine, the temperature at the Observatory rose to a maximum of 34.2 degrees on the afternoon of 30 September, the highest of the month.

Seven tropical cyclones occurred over the South China Sea and the western North Pacific in September 2026.

Details of issuance and cancellation of various warnings/signals in the month are summarised in Tables 1.1 to 1.5. Monthly meteorological figures and departures from normal for September are tabulated in Table 2.


 

Warnings and Signals issued in September 2026

Table 1.1   Tropical Cyclone Warning Signals

Name of Tropical Cyclone	Signal Number	Beginning Time		Ending Time
		Day/Month	HKT	Day/Month	HKT
SAUDEL	1	31 / 8	1810	4 / 9	0010

Table 1.2   Strong Monsoon Signal

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
12 / 9	2300	13 / 9	1345

Table 1.3   Thunderstorm Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
1 / 9	0930	1 / 9	1330
1 / 9	1950	1 / 9	2200
7 / 9	1255	7 / 9	1545
10 / 9	0205	10 / 9	0445
13 / 9	1627	13 / 9	1730
14 / 9	0950	14 / 9	1430
14 / 9	1830	14 / 9	2400
15 / 9	0442	15 / 9	1100
21 / 9	0710	21 / 9	0820
22 / 9	1100	22 / 9	1400
22 / 9	1403	22 / 9	1600
23 / 9	0805	23 / 9	1000

Table 1.4   Fire Danger Warnings

Colour	Beginning Time		Ending Time
	Day/Month	HKT	Day/Month	HKT
Yellow	19 / 9	0600	19 / 9	2300
Yellow	20 / 9	0600	20 / 9	2220
Yellow	25 / 9	0600	27 / 9	1830

Table 1.5   Very Hot Weather Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
8 / 9	0645	8 / 9	1830
12 / 9	1535	12 / 9	1730
19 / 9	1300	19 / 9	1745
20 / 9	0730	20 / 9	1745
21 / 9	1415	21 / 9	1745
25 / 9	1100	25 / 9	1730
26 / 9	0645	26 / 9	1730
27 / 9	0645	27 / 9	1745
28 / 9	1115	1 / 10	1830

Table 2   Figures and Departures from Normal - September 2026

Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	31.8 degrees C	1.3 degrees above normal
Mean Air Temperature	28.8 degrees C	0.9 degrees above normal
Mean Daily Minimum Air Temperature	27.1 degrees C	1.0 degrees above normal
Mean Dew Point Temperature	23.6 degrees C	normal
Mean Relative Humidity	74 %	4 % below normal
Mean Cloud Amount	64 %	2 % below normal
Total Rainfall	94.3 mm	227.1 mm below normal
Number of hours of Reduced VisibilityΔ	3 hours	55.8 hours below normal§
Total Bright Sunshine Duration	223.9 hours	49.5 hours above normal
Mean Daily Global Solar Radiation	18.73 Megajoule / square metre	3.74 Megajoule above normal
Total Evaporation	134.0 mm	11.2 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 2025

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 September 2026