The Observatory issued the Strong Wind Signal No 3 on Wednesday at 6.40pm. The forecaster said the signal would remain in force until at least noon.
The Education Bureau on Thursday morning announced that classes of kindergartens, schools for children with physical disability and schools for children with intellectual disability are suspended today.
Severe Typhoon Yagi was forecast to move west at about 10 kilometres per hour across the northern part of the South China Sea and intensify gradually.
The Observatory also said that if Yagi continues to intensify, local winds are expected to further strengthen later.
The Observatory said it may need to issue higher tropical cyclone warning signals between Thursday afternoon and Thursday night.