Short answer. The SCDF Public Warning System is a network of sirens with three signals: Alarm (wailing), All Clear (continuous) and Important Message (pulsating) 12. The Important Message signal is tested islandwide every 15 February and 15 September at 6:20pm, also on the SGSecure app 14. SG Alert, a cell broadcast system needing no app, is being rolled out: StarHub by end-2026, M1 and SIMBA by mid-2027 3.
What are the three siren signals?
| Signal | Sound | Meaning | What to do |
|---|---|---|---|
| Alarm | Wailing blasts | An air raid or danger is approaching | Move to a Civil Defence shelter immediately |
| All Clear | Continuous blasts | The threat is over | Leave the shelter in an orderly manner |
| Important Message | Pulsating blasts | An important message will be broadcast on local free-to-air FM radio and TV and emergency notification systems | Tune in immediately to local free-to-air FM radio and TV, phone notifications (SGSecure, SG Alert) and SCDF's social media |
Source: SCDF Civil Defence Emergency Handbook, 2026 2.
When are the sirens tested?
The Important Message signal is sounded islandwide twice a year, on 15 February (Total Defence Day) and 15 September, at 6:20pm, for about one minute 12. At the same time, the SGSecure app sounds a 20-second signal with a short text message 14. A test on those dates needs no action beyond knowing the sound.
What is SG Alert?
SG Alert is SCDF's cell broadcast system, "a mass emergency alert system for use during emergencies" 3. What SCDF states about it 3:
- No app, registration or mobile data is needed, and no personal data is collected.
- Phones need iOS 26.4 or later, or Android 12 or later with the latest Google Play system update.
- Alerts bypass silent and Do Not Disturb modes and cannot be switched off.
- Alerts are sent in English, plus Mandarin, Malay or Tamil if the phone is set to that language.
Rollout is phased: StarHub's network by end-2026, then M1 and SIMBA by mid-2027 3. Until your network is covered, rely on the sirens, the SGSecure app and broadcast media.
Which apps carry official alerts?
- SGSecure (Ministry of Home Affairs): alerts during major emergencies, 999 calls and SMS to the Police 4.
- myResponder (SCDF) 2.
When phone networks are unreliable, a radio still receives free-to-air FM broadcasts. Our guide Which radio and alerts do you need when networks are down? covers the options.
What should I do when I hear the Alarm?
Move to a Civil Defence shelter immediately 2: the household or storey shelter at home, or the nearest public shelter. The handbook also says that, for homes without a shelter, it would be relatively safer to stay home under improvised cover than to move out to a public shelter during an attack 2. See Public shelters in Singapore.
Frequently asked questions
Why do sirens sound on 15 February?
15 February is Total Defence Day, one of the two dates when the Important Message signal is tested islandwide at 6:20pm 12.
Can I turn off SG Alert messages?
No. SG Alert messages cannot be switched off and bypass silent and Do Not Disturb modes 3.
Do I need to register for SG Alert?
No. It needs no app, registration or mobile data, but your phone and network must be supported 3.
What does the pulsating siren mean?
It is the Important Message signal: tune in immediately to local free-to-air FM radio and TV, phone notifications and SCDF's social media 2.
Sources
- Singapore Civil Defence Force (SCDF) — Public Warning System — https://www.scdf.gov.sg/home/civil-defence-shelter/public-warning-system (accessed 2026-10-20)
- Singapore Civil Defence Force (SCDF) — Civil Defence Emergency Handbook (10th edition, 2026) – English — https://www.scdf.gov.sg/docs/default-source/comm.---volunteers-(docs)/2026-scdf-emergency-handbook(eng)_16-oct.pdf (accessed 2026-10-20)
- Singapore Civil Defence Force (SCDF) — Emergency Alert (SG Alert) — https://www.scdf.gov.sg/home/civil-defence-shelter/emergency-alert-(sg-alert) (accessed 2026-10-20)
- SGSecure / Ministry of Home Affairs — SGSecure App — https://www.sgsecure.gov.sg/resources/app (accessed 2026-10-20)
Turn this into action
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Sources
- Singapore Civil Defence Force (SCDF) · Public Warning System checked 2026-10-20
- Singapore Civil Defence Force (SCDF) · Civil Defence Emergency Handbook (10th edition, 2026) – English checked 2026-10-20
- Singapore Civil Defence Force (SCDF) · Emergency Alert (SG Alert) checked 2026-10-20
- SGSecure / Ministry of Home Affairs · SGSecure App checked 2026-10-20