The Hong Kong Observatory issued the first typhoon signal Number 8 of the year at 6.20pm on Thursday as Super Typhoon Yagi moved closer to Hong Kong.

The weather forecaster said the Number 8 northeast gale or storm signal is expected to be in place until at least noon on Friday.

"Yagi is a mature storm. Under the influence of its outer circulation, strong winds will affect many places of the territory with occasional gale winds offshore and on high ground," the observatory said.

It added that local winds would strengthen progressively and the weather would deteriorate on Thursday evening.

According to the present forecast, Yagi will remain at super typhoon intensity and skirt around 300 kilometres to the southwest of the SAR on Friday morning.

The storm warning upgrade came almost 24 hours after the forecaster issued the No 3 signal.