How does the UK warn people in an emergency?

Short answer. The UK's main public warning system is Emergency Alerts, a free cell-broadcast service run by the government since 2023 ¹². Phone masts near a life-threatening emergency send the alert to every compatible 4G or 5G phone in range, with a loud siren-like sound and vibration for about 10 seconds, even if the phone is on silent ². No sign-up or app is needed ¹.

What is the UK Emergency Alerts system?

Emergency Alerts sends messages to mobile phones in an area where there is a danger to life. In the government's words: "Emergency alerts are free. You do not need to sign up for them or download an app." ¹ Trials ran in 2021 in East Suffolk and Reading, and the first UK-wide national test took place on Sunday 23 April 2023 ²⁴.

How do emergency alerts reach my phone?

Phone masts near the emergency broadcast the alert to every compatible device in range ². The system works on all UK 4G and 5G networks and needs no phone number or location data ². Compatible phones run iOS 14.5 or later, or Android 11 or later ².

You will not receive an alert on a 2G or 3G phone, on a wifi-only device, on a phone that is switched off, or on an incompatible device ².

What does an alert sound like, and what should I do?

The phone makes a loud siren-like sound and vibrates for about 10 seconds, even on silent, and the alert may be read out ². It includes a phone number or a GOV.UK link for more information ².

When you get one, stop what you are doing and follow the instructions in the alert. If you are driving, find somewhere safe and legal to stop before reading it ². Alerts are in English, and in Wales also in Welsh ².

Who can send an alert?

The emergency services and the government departments, agencies and public bodies that deal with emergencies ². GOV.UK/Prepare also names devolved governments, the police and local councils ⁵.

Has the UK used it for real?

Yes. Examples listed by the government include red wind warnings for Storm Éowyn (23 January 2025, Scotland and Northern Ireland), an alert for Cornwall and the Isles of Scilly (8 January 2026), and a national wildfire risk alert for England and Wales (14 August 2026) ³.

Is there a national test day?

There is no fixed annual test day. National tests were held on 23 April 2023 and 7 September 2025 ²³.

Does the UK have public sirens?

No national public siren network is described in government guidance. Some local Environment Agency flood warning sirens exist in high-risk areas; those in the Calder Valley were tested in September 2023 ⁶. Warning arrangements around nuclear and industrial sites may be set out in local off-site emergency plans; Phaenyx has not verified this, so check with your local council.

What other official warnings can I sign up for?

No app is needed for Emergency Alerts. GOV.UK/Prepare lists other official warnings you can sign up for: Environment Agency flood warnings, Met Office email alerts, the UKHSA Weather-Health Alerting System (England), air quality alerts, and some Local Resilience Forum alerts ⁵.

Frequently asked questions

Do I need to register for UK emergency alerts?

No. Alerts are free, and you do not need to sign up or download an app ¹.

Will an alert sound if my phone is on silent?

Yes. The siren-like sound and vibration last about 10 seconds even if the phone is on silent ².

Why didn't my phone receive the alert?

Alerts are not received on 2G or 3G phones, wifi-only devices, phones that are switched off, or incompatible devices. Compatible phones run iOS 14.5 or later, or Android 11 or later ².

Is the alert in Welsh?

In Wales, alerts are sent in English and Welsh ².

Sources

1. UK Government (GOV.UK Emergency Alerts) — About Emergency Alerts — https://www.gov.uk/alerts (accessed 2026-10-20)
2. UK Government (GOV.UK Emergency Alerts) — How emergency alerts work — https://www.gov.uk/alerts/how-alerts-work (accessed 2026-10-20)
3. UK Government (GOV.UK Emergency Alerts) — Past alerts — https://www.gov.uk/alerts/past-alerts (accessed 2026-10-20)
4. Cabinet Office — Frequently asked questions about Emergency Alerts — https://assets.publishing.service.gov.uk/media/64161410d3bf7f79df1aaa19/Frequently_asked_questions_about_Emergency_Alerts.pdf (accessed 2026-10-20)
5. Cabinet Office (GOV.UK Prepare) — Alerts and warnings — https://prepare.campaign.gov.uk/get-prepared-for-emergencies/alerts/ (accessed 2026-10-20)
6. Environment Agency (GOV.UK) — Calder Valley flood warning sirens tested (25 September 2023) — https://www.gov.uk/government/news/calder-valley-flood-warning-sirens-tested (accessed 2026-10-20)