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Leopold Chen

Hong Kong has issued 51 rainstorm warnings so far this year, including four top-tier signals, surpassing a record held for the whole of 2001, the Post has found.
The record was broken at 11.45am on Wednesday when an amber rainstorm warning signal was raised.
Four black rainstorm warnings issued in the past week were in effect for a combined 17 hours and 35 minutes, a record high for the duration of the signals in a single summer since the system was revamped in 1998.
But a veteran meteorologist warned that global warming could mean more instances of extreme wet weather in Hong Kong were likely to occur in the long run.
A check by the Post found that no signals were issued before mid-March, with five amber rainstorm warnings sent out between March 15 and June 17.
Between the summer solstice on June 21 and Wednesday, another 46 warnings of all tiers were issued. The figure for this period alone was the highest number since 1998.
The summer solstice typically falls on June 21 or 22, with the date potentially varying by one or two days each year.




The 51 warnings sent out this year have already surpassed the previous 2001 record of 50 for the entire year.
Hong Kong introduced the colour warning system for rainstorms in 1992, which was revamped to a three-tier model in 1998 and saw the green signal ditched.
The Observatory’s three-tier rainstorm warning system is based on whether heavy rain has fallen or is expected to fall generally over Hong Kong within an hour, with thresholds of 30mm for amber, 50mm for red and 70mm for black.
The current summer has already seen four black signals so far, the highest number on record and beating the three signals issued in both 2000 and 2006.


On Tuesday, a black rainstorm signal was in force for more than 11 hours until 5pm, with a total of 358.8mm of rainfall occurring, breaking the highest amount of daily rainfall for August since the Observatory’s records began in 1884.
The signal was issued at 5.50am and heralded downpours and flooding across the city. It was the second-longest black rainstorm warning on record, only beaten by the signal issued on September 7, 2023, which lasted for 16 hours and 35 minutes.
The rainy summer followed a dry first half of the year, with the accumulated rainfall from January to June being just 444.4mm, 41 per cent of the normal level of 1,082.5mm for the same period.
In July alone, however, the amount of rainfall reached 601.7mm, about 56 per cent above the norm of 385.8mm.


Leung Wing-mo, a former assistant director at the Observatory, said this summer’s heavy rainfall was most likely to be a coincidence, but noted global warming could also have played a role.
“The change of weather itself is of much variability. We may have several years without one black rainstorm warning, or several such warnings in one year,” he said.
“However, because of climate change, such variability will be more acute.”
While it was difficult to predict rainfall levels or their intensity for the coming years based on the current situation, Hong Kong could gradually see more such rainstorms by the end of the century due to global warming, Leung said.
According to the Observatory, under the intermediate level of greenhouse gas emissions, the annual rainfall in Hong Kong is expected to be 7 per cent higher around the end of the century compared with the average level between 1995 and 2014.
Leung explained that this was because the warmer air could hold more humidity.
“As long as the level of carbon dioxide does not reduce, this is set to happen,” he said.


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News

Weather

Hong Kong

Veteran meteorologist warns that global warming could mean more instances of extreme wet weather in Hong Kong are likely to occur in long run


Veteran meteorologist warns that global warming could mean more instances of extreme wet weather in Hong Kong are likely to occur in long run.


Leung Wing-mo

Hong Kong issued 51 rainstorm signals for 2025 so far, beating whole-year record

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Veteran meteorologist warns that global warming could mean more instances of extreme wet weather in Hong Kong are likely to occur in long run

Veteran meteorologist warns that global warming could mean more instances of extreme wet weather in Hong Kong are likely to occur in long run