**Nationwide Emergency Siren to Sound Across UK Mobile Phones in September Test**
In a move to strengthen national preparedness for emergencies, the UK government has announced the date and time when a countrywide emergency siren will be simultaneously broadcast to mobile phones across the United Kingdom. Scheduled for 3pm on Sunday, 7 September, this coordinated test marks only the second time the nationwide Emergency Alerts system will be trialled, following its introduction last year.
During the exercise, every compatible mobile phone will emit a distinctive, ten-second siren and vibrate, regardless of whether they are set to silent mode. In addition to the audible warning, a notification will flash on device screens, explicitly stating that the incident is merely a test and does not indicate real danger.
The Emergency Alerts system is a government initiative designed to provide rapid, critical information during life-threatening situations such as severe weather or other emergencies. Officials have stressed that this capability could prove vital in alerting the public to imminent hazards and giving timely advice to limit risk and protect lives.
It is estimated that up to 87 million mobile devices are currently in use across the UK, underscoring the potential scale and reach of this technology. The system, which operates on all 4G and 5G networks, does not require users to be connected to mobile data or WiFi to receive messages. However, alerts will not reach devices that are switched off, limited to 2G or 3G coverage, set to WiFi-only mode, or are otherwise incompatible.
According to government sources, neither emergency services nor government departments need to know individuals’ phone numbers to deliver these alerts, as notifications are broadcast to all active devices within affected areas through cell towers. This practice is consistent with protocols established in countries such as the United States and Japan, where similar alert systems have become a routine aspect of disaster response.
As the scheduled test approaches, authorities have committed to running a public information campaign, targeting not only the general population but also particularly vulnerable groups. Notably, support organisations have raised concerns about individuals at risk of domestic abuse who may own concealed mobile devices. The government has indicated it will address these potential safety implications in its broader communications strategy.
Pat McFadden, Chancellor of the Duchy of Lancaster, commented on the importance of the alert system, likening its presence to a household fire alarm: “Emergency Alerts have the potential to save lives, allowing us to share essential information rapidly in emergency situations including extreme storms. Just like the fire alarm in your house, it’s important we test the system so that we know it will work if we need it.”
Since the initial test in April 2023, the Emergency Alerts system has been activated five times in response to real emergencies. This includes messages broadcast at the peak of major storms where weather agencies issued the highest level of danger warnings. For instance, during Storm Éowyn in January 2025, approximately 4.5 million residents in Scotland and Northern Ireland received simultaneous alerts as red warnings—signifying threat to life—were posted. Similarly, around 3.5 million were notified during Storm Darragh in Wales and south west England in December 2024.
Beyond natural disasters, the system has also proved adaptable for more localised incidents, such as during the evacuation necessitated by the discovery of an unexploded World War II bomb in Plymouth, as well as urgent warnings for sudden flash flooding in counties including Cumbria and Leicestershire.
Full details of the message contents for the upcoming September test will be released in advance. Authorities hope the exercise not only verifies the technological reliability of the service but also increases public awareness and understanding of what to expect in the event of a genuine emergency.
While the government views this technology as an important step in protecting the public, it is keen to emphasise that this and future tests are standard practice. Regular drills, officials argue, are essential to ensuring that such systems deliver under pressure and that the population knows exactly how to respond—should the need ever arise.