The torrential downpours that soaked Hong Kong this week coincided with a rainmaking operation in which aircraft sprayed chemicals on clouds blanketing Shenzhen.
More than 400mm of rain fell in Hong Kong between Sunday and Tuesday, leaving the territory's reservoirs 90 per cent full, even though the Observatory initially forecast only scattered showers.
Over the same period, officials in Shenzhen sent planes into the sky to distribute rain-inducing chemicals, a process known as cloud seeding, prompting speculation that it may have caused Hong Kong's downpours.
The Hong Kong China News Agency said that the authorities in Shenzhen carried out the operation because they were concerned about drought conditions in some of its neighbouring areas.
Residents in Shenzhen were deluged with rain over the same three-day period this week.
One of them, a 28-year-old accountant, said yesterday: 'We read about the rainmaking operation and a lot of people have been wondering if the very heavy rain is because of it.
'We heard Hong Kong had been getting some of the same weather and we suspect the whole process might have worked better than the people responsible expected it to.'