Hong Kong faces record-breaking October heat wave driven by three factors
Hong Kong issued a Very Hot Weather Warning on 21 October as temperatures neared 33°C. A professor from Chinese University attributed the heat to Super Typhoon Champi’s subsiding air, a Super El Niño weakening the monsoon, and global warming. The warning may break the record for latest issuance.
The Hong Kong Observatory issued a Very Hot Weather Warning at 6.45am on Wednesday as late-October temperatures soared to around 33 degrees Celsius in urban areas, with parts of the New Territories recording even higher figures.
The temperature is expected to break the record for the latest issuance of a Very Hot Weather Warning in a year, previously set on 19 October 2024. If temperatures reach 33 degrees Celsius or above this Friday (23 October), it will also mark the hottest Frost's Descent solar term on record, surpassing the previous record of 31 degrees Celsius set in 2006.
Amos Tai Pui-kuen, professor and deputy chair of the Department of Earth and Environmental Sciences at the Chinese University of Hong Kong, explained on a radio programme on Wednesday morning that this unseasonable heat wave is caused by the compounding effects of three major factors.
First, the outer subsiding air currents from Super Typhoon Champi, located about 1,040 kilometres east-northeast of Manila as of 8am this morning, coupled with an anticyclonic aloft over Hong Kong, led to sinking air and weakened winds. This reduced cloud cover and rainfall, allowing intense sunlight to directly heat the city.
Second, a Super El Niño altered tropical circulation patterns, creating an anomalous anticyclonic circulation over the South China Sea and the Philippines. This suppressed convective activity and significantly weakened the northeast monsoon that typically cools the region in autumn. With the monsoon's cooling effect drastically reduced, heat easily accumulated locally. Additionally, El Niño tends to push typhoon paths further north, away from Hong Kong; however, due to extremely high sea surface temperatures, any approaching typhoon will evaporate more moisture and heat, fueling the storm's intensity.
Third, global warming has raised the overall baseline temperature. When short-term weather anomalies and climate phenomena are superimposed on a baseline that is already warped by global warming, temperatures rise significantly above historical averages.
Tai added that the impact of the Super El Niño is expected to persist through next spring, meaning Hong Kong is likely to experience an unseasonably warm winter.