A visual system of tropical cyclone warning signals in the shape of drums and cones was in place to inform masters of vessels leaving the port of Hong Kong about the position and movement of typhoons.
This system was replaced by a ten-symbol system in 1917. The numbers were from 1 to 7 with numbers 2 to 5 signifying gale force winds expected from the northwest, southwest, northeast and southeast quadrants respectively.
In 1931, the signals were changed to 1, 5, 6, 7, 8, 9 and 10 with signals 5 to 8 signifying gales from the four quadrants.
In 1956, the No. 3 Strong Wind Signal was introduced between the No. 1 Standby Signal and the gale signals. Since 1973, the current system comprising 1, 3, 8 NW, 8 SW, 8 NE, 8 SE, 9 and 10 has been in use.
The visual display of typhoon warning signals was completely dispensed with in June 1961.