Hong Kong tropical cyclone warning signals are issued by the Hong Kong Observatory to warn of a potential threat or effects of a tropical cyclone in the greater Hong Kong area. The signals are represented with a set of numbers and symbols. Previously, lights were also used at night.
The warning system currently in use in Hong Kong is based on a signal level from the lowest level, Standby Signal No. 1, to the highest level, Hurricane Signal No. 10. The signalled numbers may change in accordance with the conditions. Once any signal that is higher than No.3 is issued, government agencies, schools, financial markets, and most of the private sector close their operations. When Signal No. 9 or No. 10 is issued, the Mass Transit Railway (MTR) ceases operations in the above ground open-air areas of the heavy rail network, as well as suspending the Light Rail.
During large tropical cyclones such as Typhoon Hato in 2017, Typhoon Mangkhut in 2018 and Typhoon Ragasa in 2025, public transit was suspended and schools and businesses were closed.
History Beginning In May 1884, the Hong Kong Observatory began warning of surrounding tropical cyclones by notifying newspapers and telegraph companies. Later that year, the observatory implemented the first visual warning system in August. It used an arrangement of red drums, cones, and balls to indicate the presence of a tropical cyclone around Hong Kong and its relative position. The signal was hoisted on a mast in front of the Tsim Sha Tsui Police Barracks. Sailors primarily used it to help plot their course. The signal did not indicate any threat of a typhoon directly impacting Hong Kong.
In August 1884, the Hong Kong Observatory began using a typhoon gun to warn residents of hazardous wind conditions. One shot was fired to indicate when strong gales were expected. Two were fired when hurricane-force winds were expected and the gun was fired again each time the wind changed direction. Initially, the same gun was also used to announce mail deliveries from London. This caused confusion for residents, so in 1886, the use of guns for mail deliveries was discontinued.
Revised visual signal In 1890, a black colour began to be used with the drum, cone, and ball visual signal to indicate the distance of a storm from Hong Kong. Red continued to be used for storms at least 300 km away, while black was used for storms closer than 300 km.
In February 1897, the storm signals created by Admiral Robert FitzRoy in 1861 were introduced in Hong Kong with a minor modification. The modified storm warning system consisted of storm signals in the form of a cone or drum and night signals. A cone pointing upward was hoisted to warn of gales from the north or east, while a cone pointing downward warned of gales from the south or west. A drum was added to the cone when a strong gale that might reach hurricane force was expected. The night signal consisted of three differently-coloured lanterns hung on a triangular frame, pointing upwards or downwards. No lanterns were hoisted to represent the drum.
First Numbered System In 1917, Hong Kong first began using numbered signals. The new system consisted of seven signals (No.1–7). Signal No.1 was used as a standby signal, Signals No.2–5 were respectively used for gales coming from each cardinal direction (north, south, east, and west), Signal No.6 for gales of increasing force, and Signal No.7 for hurricane-force winds. Second Numbered System In 1931, the system was revised, increasing the amount of signals from 7 to 10. Signal No. 1 was still used as a standby signal,. Signal No. 2 and 3 were used for strong winds from the Southwest and Southeast respectively, however Signal No. 2 became obsolete in 1935 and No. 3 between 1935-1955 before being adopted as the current Strong Wind Signal No. 3 in 1956. Signal No. 4 was for strong typhoons that did not pose imminent danger locally, however it was not applicable to Hong Kong. Signal No. 5-8 were used for gales from the Northwest, Southwest, Northeast and Southeast respectively. Signal No. 9 replaced the old Signal No. 6 while Signal No. 10 replaced the old Signal No. 7.
History In 1917, a numbered signal system was implemented for warning wind conditions in the territory. Hong Kong island Kowloon New Territories East New Territories West Outlying islands Marine Department Signal Station, Connaught Road Central Hong Kong Observatory Rennie's Mill Police Station, Junk Bay Tsuen Wan, Caltex Depot Waglan Island Blackhead Hill Sha Tin Police Station Cheung Chau Police Station Green Island Signal Station Sai Kung Police Station Hei Ling Chau Police Station Lei Yue Mun Fort Kowloon Wharf and Godown Company Signal Tower^ Castle Peak Police Station Mui Wo Police Station, Lantau Island Tamar Kowloon Railway Station Clock Tower* Tai Po District Office Ping Shan Police Station Shek Pik Police Post, Lantau Island Kowloon Hospital, Argyle Street Tai O Police Station, Lantau Island Aberdeen Police Station Kowloon Docks, Big Crane* Sha Tau Kok, Medical Department Clinic Stanley Village Police Station Kwun Tong, Shell Oil Company Installation Pat Heung Police Station Stanley Fort (near Measured Mile Marks) Stonecutters Island, W/T mast* Lok Ma Chau Police Station Lai Chi Kok, Stanvac Installation
^ = day signals only * = night signals only
In 1963, a visual signal was completed at Lau Fau Shan Police Station in Deep Bay. Night stations were installed at the San Miguel Brewery in Sham Tseng and the Port Signal Station at North Point. In 1964, a storm signal station established at the Marine Licensing Office, Shau Kei Wan, was brought into operation. In 1965, storm signal stations, displaying both day and night signals were established at the Marine Police Operations Bases at Tai Po Kau and Tai Lam Chung, at the Plover Cove Police Station, and at Divisional Police Headquarters, Yuen Long.
Signal stations at the Mobil Oil Depot Lai Chi Kok and at Hei Ling Chau Police Station ceased operation. In 1967, a signal station was established at Peng Chau Police Station. The number of signal stations in Hong Kong peaked at 42 according to the Observatory's 1968–1969 annual report. Aberdeen Police Station was vacated in October 1969. The station at Marine Department Headquarters was moved to Port Communication Centre in April 1970. The station at Cheung Chau Police Station was moved to the meteorological station in 1971.
Closing progressively In 1983, only 15 signal stations were retained to provide visual display of signals, mainly to vessels in or near the harbour. Hong Kong island Kowloon New Territories East New Territories West Outlying islands Marine Department Port Communication Centre Waglan Island Shau Kei Wan Marine Licensing Office Cheung Chau Aeronautical Meteorological Station Green Island Signal Station Yau Ma Tei Cargo Working Area Building Sai Kung Police Station Tai Lam Chung Marine Police Operations Base Tai Po Kau Marine Police Operations Base Tamar Lau Fau Shan Police Station, Deep Bay Tai O Police Station, Lantau Island Aberdeen Marine Licensing Office Sha Tau Kok Police Post Stanley Village Police Station
The signal stations at Waglan Island and Marine Department Port Communication Centre ceased to operate with effect from 30 June 1988. The signal station at Green Island ceased to operate with effect from 15 October 1989.
Decommissioning Starting on 1 April 2000, signals would no longer be hoisted at the signal stations at Aberdeen Marine Office, Sha Tau Kok Sewage Treatment Works and Tai Lam Small Boat Unit Headquarters; from 21 April 2001, signals would no longer be hoisted at the signal station at Lau Fau Shan Police Station; and from 1 January 2002, signals would no longer be hoisted at the signal station at Cheung Chau Aeronautical Meteorological Station.
Current system
In accordance with legal codes and customs in Hong Kong, once any signal higher than No. 3 is issued, all government agencies shut down their operations. Schools, financial markets, and most of the private sector closes. Non-essential workers are released from work in a staggered manner so as to avoid overwhelming public transportation. Public transit agencies generally continue to operate initially but may cease operation at short notice. The Hong Kong Observatory has since 1987 issued warnings two hours in advance of the issuance of the No. 8 warning signal.
Criticism In its early days, the system relied upon wind speeds measured around Victoria Harbour. As the emphasis shifted to serving the urbanised populace, such observations were seen as lacking relevance. The Hong Kong Observatory was criticised during Typhoon Prapiroon in 2006, when conditions in urban areas were much more severe than those on the harbour, which had justified only a No. 3 signal being issued. In response, in 2007, the Hong Kong Observatory broadened its network to eight near-sea-level reference anemometers around Hong Kong.
According to the new system, the No.3 and No.8 signals will be issued when half or more anemometers in the reference network register sustained winds of and respectively. In 2013, Lau Fau Shan replaced Wetland Park as a reference anemometer station. The current eight reference anemometer stations include Cheung Chau, Hong Kong International Airport, Sai Kung, Kai Tak, Lau Fau Shan, Tsing Yi Shell Oil Depot, Sha Tin, and Ta Kwu Ling.
Signal No. 10 occurrences
When Typhoon Hato hit Hong Kong in August 2017, Signal No.10 was issued, leading to flights being suspended or cancelled. Flights later resumed as soon as it was safe, including throughout the night to make up for lost time. MTR cancelled train services in open sections of the line and maintained a limited service underground on an adjusted schedule. All schools were closed for the day, and the government opened temporary shelters. Trees fell and flooding occurred. The stock market (and other businesses) were suspended for part or a whole day.
When Typhoon Mangkhut hit Hong Kong in September 2018 with Signal No.10 being issued, all of the aforementioned closure happened. The Hong Kong Observatory and the Hong Kong Government advised people to put masking tape on their windows to try and stop their windows from being blown away.
2025 saw Signal No.10 issued twice that year, the first time being on July 20 when Tropical Storm Wipha was preparing to make landfall. Over 500 flights were cancelled as a result, along with the MTR limiting services. The second instance occurred on September 24, at 02:40 HKT, when Signal No.10 was issued for Typhoon Ragasa, while the storm was 120 km (75 mi) from Hong Kong. This made Ragasa the furthest typhoon from Hong Kong to ever trigger the signal and the first time that Signal No.10 was triggered when a storm was more than 100 km (62 mi) away from Hong Kong, surpassing the old record of 100 km held jointly by Typhoon Mangkhut in 2018 and Typhoon Vicente in 2012. The Signal No.10 was in force for 10 hours and 40 minutes, second only to the record of 11 hours set during the passage of Tropical Storm York in 1999.
Meaning of signals The Saffir–Simpson hurricane wind scale is a classification used for some Western Hemisphere tropical cyclones. Hong Kong has similar official five-level definition warning signals, which use descriptions of winds taken from the Beaufort Scale. The Hong Kong levels, however, do not correspond to the Beaufort Scale, which has 12 levels.