Due to the stronger than usual subtropical ridge over southern China, last month was the hottest September in Hong Kong on record, the Hong Kong Observatory said today.

The monthly mean maximum temperature, monthly mean temperature and monthly mean minimum temperature were 32.8 degrees Celsius, 29.7 degrees Celsius and 27.8 degrees Celsius, making all of them the highest on record for September.

There were 15 very hot days and 11 hot nights in the month, both setting new records for September. In addition, the numbers of very hot days and hot nights from January to September have already reached 53 days and 57 days, both exceeding the annual figures in 2020.

With plenty of sunshine and under the influence of super typhoon Chanthu’s outer subsiding air, the temperature on September 12 soared to 34.5 degrees Celsius, the peak of the month. The daily mean temperature on that day was 31.2 degrees Celsius, a joint highest on record for September.

Meanwhile, last month was much drier than usual as the total rainfall was 129.6mm, about 40% of the normal figure. However, localised heavy showers and thunderstorms occurred on September 16. More than 100mm of rainfall was logged in Tseung Kwan O where hail was also reported.

Five tropical cyclones occurred over the South China Sea and the western North Pacific in September, the Hong Kong Observatory added.