What Do Hong Kong's No. 8 and No. 10 Typhoon Signals Mean? Comparison with Mainland China's Blue, Yellow, Orange and Red Warnings
Why Is It Called "Hoisting a Typhoon Signal" in Hong Kong?
Since 1917, the Hong Kong Observatory has used numbered tropical cyclone warning signals. In the early days, physical symbols of different shapes (commonly called "typhoon balls") were displayed at signal stations in the harbor to warn ships and the public. Although these signals are now issued entirely through electronic means, the expressions "hoisting the No. 8 signal" and "dropping the balls" have become part of everyday life for people in Hong Kong, Macao and Guangdong.
Comparison of Hong Kong's Five Typhoon Signal Levels with Mainland China's Four Warning Levels
| Hong Kong Observatory Signal | Sustained Wind Criteria | Equivalent Beaufort Wind Scale | Corresponding Mainland China Warning | School and Work Suspensions and Transport Arrangements |
|---|---|---|---|---|
| Standby Signal No. 1 (T1) | A tropical cyclone has formed within approximately 800 km of Hong Kong | Standby status | Blue typhoon warning (early warning) | Normal work and school schedules; monitor the Hong Kong Observatory's updates |
| Strong Wind Signal No. 3 (T3) | Sustained winds of 41–62 km/h | Force 6–7, strong winds | Blue/yellow typhoon warning | Kindergartens and special schools are closed; outdoor work at height is suspended |
| Gale or Storm Signal No. 8 (T8) | Sustained winds of 63–117 km/h, with gusts exceeding 180 km/h | Force 8–11, gale or storm | Yellow/orange typhoon warning | All schools are closed, most businesses suspend operations, the Hong Kong Stock Exchange is closed, and buses and ferries are not operating |
| Increasing Gale or Storm Signal No. 9 (T9) | Gale or storm winds are increasing significantly | Force 10–11, intensifying storm | Orange/red typhoon warning | Above-ground sections of the MTR suspend operations immediately, and the public is strictly advised not to go out |
| Hurricane Signal No. 10 (T10) | Sustained winds of ≥118 km/h, with gusts exceeding 220 km/h | ≥Force 12, hurricane | Red typhoon warning | Maximum defensive measures are in place as the typhoon's eyewall passes directly over Hong Kong or makes landfall |
Why Does the "No. 8 Signal" Come in Four Directions (Northeast, Northwest, Southeast and Southwest)?
Attentive readers may notice that the No. 8 signal is divided into four subsignals: No. 8 Northeast, No. 8 Northwest, No. 8 Southeast and No. 8 Southwest. This is because Hong Kong is highly mountainous, and wind from different directions affects the various harbors and residential areas in very different ways. When a typhoon passes south of Hong Kong, the wind direction often shifts from northeast to southeast. The Observatory then issues a No. 8 signal for the new wind direction to remind the public that "a window previously sheltered from the wind may soon face the full force of the wind."
How Rare Has the No. 10 Signal Been in Hong Kong's History?
Since 1946, the Hong Kong Observatory has issued the Hurricane Signal No. 10 only once every four to five years on average. Notable typhoons that have resulted in the No. 10 signal in recent years include VICENTE in 2012, HATO in 2017, MANGKHUT in 2018, SAOLA in 2023 and YAGI in 2024 (No. 8 signal). In 2018, super typhoon MANGKHUT brought down more than 60,000 trees across Hong Kong and shattered the glass curtain walls of numerous buildings, making it one of the worst wind disasters in Hong Kong since the end of World War II.