With the summer flu season now at an end, health authorities are advising people to get vaccinated for the winter even if they caught the flu during the summer season.

Speaking on an RTHK programme, Centre for Health Protection controller Edwin Tsui noted the predominance of influenza A led to 25 severe paediatric and 507 severe adult cases which caused 342 deaths during the summer flu season.

"As influenza always mutates, we need to get vaccinated every year. The predominant strain in the summer season was influenza A, but we don't know if this will change to another strain during the winter season," Tsui said.

"People should be vaccinated even if they caught influenza in the summer season, so they can also be protected from other influenza strains in the winter season," he added.

As Tsui predicts the winter flu season may come after the Lunar New Year school holiday, he reminded schools to pay attention to the health of their students when they return to class after the break.

Schools should also maintain good hygiene, ventilation and remind children to wash their hands to reduce the chance of a flu outbreak, he said.

He added the winter influenza season generally runs from January to March, with activity expected to rise again as the weather turns colder.

Affected by the winter monsoon, temperatures in many areas fell to around 12 degrees on Friday morning, and with clear skies, radiative cooling was particularly significant in parts of the New Territories, where the temperature dropped below seven degrees.

At 8am, Ta Kwu Ling recorded a minimum temperature of only 1.9 degrees, while the temperature was 3.2 degrees at Pak Tam Chung and 6.1 degrees at Sheung Shui.