A cold front forming over central China was expected to move south over the weekend, bringing in cooler temperatures below 20 degrees Celsius (68 degrees Fahrenheit) for the first time this autumn, the Hong Kong Observatory said on Wednesday.
While showers were also expected, a weather expert said people would not need to dig out winter coats just yet.
Hongkongers are likely to experience lower temperatures on Friday and Saturday, ranging between 18 degrees and 22 degrees. Forecasters also predict it to be cooler on Sunday, with a high of 24 degrees and a low of 19 degrees during the day.
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The lowest temperature recorded in September this year was 26 degrees.
“It will be cooler with a few rain patches in the following couple of days, and temperatures will be below 20 degrees in the morning,” the Observatory said.
Leung Wing-mo, the Observatory’s former assistant director, said Hong Kong was likely to suffer from “hotter and longer summers” because of global warming.
“Summers are getting longer at the expense of winter coming late year after year under the trend of global warming. There’s nothing we can do about it except by reducing carbon emissions,” Leung said.
The cooler temperatures over the weekend would be “comfortable”, he said, adding that the “chances of wearing winter clothes right now are not as high” as they would have been at this time of year about a decade ago.
He also warned that persistent high temperatures for longer periods meant people would be inclined to use their air-conditioning more often as well, worsening the issues of global warming and failing to curb carbon emissions.
According to the Observatory’s seasonal forecast, the impact of global warming and local urbanisation means that autumn temperatures show a “significant long-term rising trend” in Hong Kong.
This year, Hong Kong faced its hottest September on record – the month when autumn usually sets in – and the city saw a monthly mean temperature of 29.7 degrees.
A total of 15 very hot days and 11 hot nights were recorded that month.
Forecasters in the city define very hot days as those when temperatures rise to 33 degrees and above, while hot nights are defined as having a temperature that does not drop below 28 degrees.
Two back-to-back typhoons lashed the city in early October after the record-breaking September heat.
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