Hong Kong will likely experience nine to 17 cold weather days this winter, meaning temperatures will fall to 12 degrees or below, according to the observatory.

However, acting assistant director Tse Shuk-mei told RTHK on Tuesday that temperatures overall will range between normal and above-normal throughout the season.

This is because winter temperatures in the city are showing a significant increasing trend over the long term, due to global warming.

With the mercury starting to fall appreciably these days, Tse said, the public should avoid staying in windy places for too long.

"These days, winds from the north are quite strong, and the observatory's special weather tips also said that the wind chill effect will be rather significant," she said.

"This means that when the winds are strong, it is easier for heat to be carried away from the body, which will make us feel colder than the actual ambient temperature. Therefore, do not linger for too long in windy conditions."

As for the elderly, Senior Citizen Home Safety Association chief executive Maura Wong emphasised that exercise was crucial to keep warm.

"They might choose not to go out when winds become stronger or during cold weather. Even if they are not heading out, we suggest the elderly exercise indoors," she said.

"Because if they don't do so, their blood will not flow well, making them more liable to fall and feel cold."

Maria Leung from the Hospital Authority's Coordinating Committee in Family Medicine warned that the cold weather could trigger a worsening in the conditions of high-risk groups, including those with heart or chronic lung diseases, as their veins and trachea would constrict.

She went on to say that as the flu virus is also more active in cold weather, people in such high-risk groups should stay warm and get vaccinated against influenza as soon as possible.