Hottest September with record-breaking numbers of very hot days and hot nights

Hottest September with record-breaking numbers of very hot days and hot nights

Hui Kin-chung

Mainly as a result of the stronger-than-usual subtropical ridge over southern China, September 2021 was Hong Kong’s hottest September on record. The monthly mean maximum temperature of 32.8 °C, monthly mean temperature of 29.7 °C and monthly mean minimum temperature of 27.8 °C were all the highest on record for September. There were in total 15 very hot days and 11 hot nights in the month, both breaking the records for September. Moreover, from January to October, the numbers of very hot days and hot nights in 2021 already reached 54 days and 61 days, respectively – both breaking the previous records set in 2020.

Long-term time series of mean temperature in September in Hong Kong