With much sunnier weather than usual in the month, September 2022 was exceptionally hot in Hong Kong. The monthly mean maximum temperature of 32.7 degrees, the mean temperature of 29.6 degrees and the mean minimum temperature of 27.3 degrees were 2.2 degrees, 1.7 degrees and 1.2 degrees above their corresponding normals respectively and all of them were the second highest on record for September. There were three days with daily maximum temperatures at the Hong Kong Observatory equal to or higher than 35.0 degrees in the month, the highest number on record for September. The total duration of bright sunshine of 237.4 hours in the month was about 36 per cent higher than the normal of 174.4 hours and the eighth highest on record for September. The month was also drier than usual with a monthly rainfall of only 171.2 millimetres, about 53 per cent of the normal of 321.4 millimetres. The accumulated rainfall this year up to September was 1,999.0 millimetres, about 11 per cent lower than the normal figure of 2,242.8 millimetres for the same period.
 
     Under the influence of a weak northeast monsoon, it was very hot with sunny periods on the first day of the month in Hong Kong. High temperatures also triggered thundery showers over the territory in the afternoon. More than 70 millimetres of rainfall were recorded over Tai Po and North District of the New Territories. Affected by a dry continental airstream, the weather of Hong Kong was fine and dry on September 2 to 6. It was also very hot during the day on September 3 to 6.  
 
     Under the influence of an easterly airstream along the coast of Guangdong and a broad trough of low pressure over the South China Sea, local weather turned mainly cloudy with occasional showers and a few thunderstorms on September 7. More than 20 millimetres of rainfall were recorded over many places in the New Territories and rainfall even exceeded 40 millimetres in Tai Po. Dominated by a ridge of high pressure, apart from isolated showers, it was generally fine and very hot during the day on September 8 and 9. Under light wind conditions, apart from sunny intervals, high temperatures triggered a few showers the next day.
 
     With the prevalence of a dry continental airstream, apart from a few showers, the weather of Hong Kong was generally fine and very hot on September 11 to 17. It was also very dry during the day on September 13 to 15 and there was some haze on September 12 and 13 and September 16 and 17. With plenty of sunshine, the maximum temperature at the Observatory soared to 35.9 degrees on September 13, the highest of the month and the highest maximum temperature for September on record. Moreover, the daily mean temperature at the Observatory reached 31.7 degrees on September 13 and 14, the highest on record for September. The daily minimum temperature of 29.6 degrees on September 14 was also the highest on record for September.
 
     Under light wind conditions, apart from sunny periods on September 18 and 19, high temperatures triggered a few showers and squally thunderstorms over the territory on these two days. In particular, the isolated severe squally thunderstorms on the afternoon of September 18 brought intense gusts to Sai Kung, Lau Fau Shan and Tai O. With the onset of a fresh to strong northeast monsoon, there were sunny intervals and a few showers on September 20. Apart from a few morning showers, the weather of Hong Kong turned generally fine on the next two days.
 
     With the arrival of a replenishment of the northeast monsoon, local weather was mainly fine at first but became cloudy gradually with a few showers and thunderstorms later on September 23. More than 20 millimetres of rainfall were recorded over the western part of the New Territories. Under the influence of the drier northeast monsoon, apart from a few showers, it was generally fine and dry on September 24 to 26. Local weather turned cloudier and windier on September 27 and 28. Affected by a broad trough of low pressure, it was mainly cloudy with showers and squally thunderstorms on September 29 and 30. Showers were heavy at times on September 30, with more than 100 millimetres of rainfall recorded over many places of the territory. Under the rain, the temperature at the Observatory dropped to a minimum of 24.8 degrees on that day, the lowest of the month.
 
     Eight tropical cyclones occurred over the South China Sea and the western North Pacific in September 2022.
 
     Details of issuance and cancellation of various warnings/signals in September are summarised in Table 1. Monthly meteorological figures and departures from normal for September are tabulated in Table 2.
 

Ends/Wednesday, October 5, 2022
Issued at HKT 16:00

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