A meteorologist has debunked an online rumour that claimed the cold winds buffeting Hong Kong could carry the coronavirus disease to the city from mainland China, where it originated.

Rumours spread as a cold front coming down from Guangdong was expected to lower temperatures this week to 10 degrees Celsius (50 Fahrenheit).

The message, which circulated on Facebook and WhatsApp, said the cold wind would bring the virus from the epicentre in Hubei province some 900 kilometres away to the south of the country, including Hong Kong.

It also claimed the air in Wuhan and its nearby cities were filled with smoke containing the virus because of the cremation of nearly a thousand people who have died from the Covid-19 disease.

The message asked Hongkongers to close their windows and stay at home with masks on until next Tuesday, when the cold air should have passed.

But Lam Chiu-ying, former director of the Hong Kong Observatory, debunked the claims on his Facebook page, and said the rumours were “totally groundless”.

“Wuhan is 900 kilometres away from Hong Kong,” he wrote. “Even if the virus could be spread by air, it would be thinned largely to the extent that people could ignore it after it had travelled a few kilometres, let alone travelling to Hong Kong.

“Besides, there is a lot of rain when the cold air moves south, so it would be washed away completely. The circulated message has no scientific basis, it’s been made-up.

“Don’t believe it, preventing the local spread of the virus is the most important thing.”

According to the Observatory, temperature in the urban areas will linger around 14 degrees on Sunday, and fall to about 12 degrees at night. It will be a couple of degrees lower in the New Territories.

It is expected to remain cold and dry over the next few days, with the minimum temperature dropping to as low as 10 degrees on Monday and Tuesday, before rising to 12 degrees on Wednesday, and 14 degrees on Thursday.