The Hong Kong Observatory warned on Tuesday evening that hail could affect the SAR after it was reported in the Pearl River Delta.

Hail was reported in Macau as authorities there called on residents to stay indoors.

In Hong Kong, the amber rainstorm warning was issued at 9:30pm.

The forecaster called on people to be alert and seek safe shelter, as violent gusts reaching 110 kilometres per hour affect the territory.

The Labour Department called on employers to avoid assigning workers to carry out electrical work, and protect the safety of those engaged in such tasks.

"Even if electrical work is carried out or electrical plant is handled at places not affected by the rainstorm, suitable safety measures must still be adopted to prevent electric shock as the air would be more humid," said a spokesperson from the department.