Previous trial saw several million people fail to receive dummy version of messages used to inform public of imminent threat to life from the likes of extreme weather or terrorism

Government’s Emergency Alerts system will undertake its second nationwide test in two months’ time, with 87 million phones around the UK sent a dummy alert message.

At about 3pm on Sunday 7 September, every phone in the country will be triggered by the system to “vibrate and make a loud siren sound for roughly ten seconds, even if they are set to silent”. This will be accompanied by a message reassuring phone users that the noise and vibration is only for test purposes.

The previous such trial exercise took place in 2023, during which a reported 7% of intended recipients failing to receive the alert – with users of the Three network, in particular, reporting issues.

The implementation of a second text is part of a wider “commitment to test the system regularly to make sure it works optimally and familiarise the public with the alerts”, according to the government.

In the 27 months since the last test took place, the five real-life alerts have been issued, including a warning to 4.5 million people in Scotland during Storm Éowyn in January 2025. In the prior month, Storm Darragh – which ultimately caused the deaths of two people – led to 3.5 million citizens in Wales and the South West being alerted to the risks posed.

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Alerts have also been issued in relation to flash floods in Cumbria and Leicestershire, as well as an incident in which residents of Plymouth were warned following the discovery of an unexploded World War II bomb.

The system is designed to send messages to applicable devices within range of designated mobile network masts. Alerts will be issued in circumstances where there is considered to be an imminent threat to life or safety – primarily from extreme weather, such as heat, cold, storms, or wildfires. Other uses might include acts of terrorism or other incidents that threaten public safety.

Before the test in September, the government has indicated that it will roll out “a public information campaign to notify people that the test is taking place, including communications targeted at vulnerable groups, such as victims of domestic abuse”. This initiative will also deliver comms in British Sign Language.

Pat McFadden, chancellor of the Duchy of Lancaster, said: “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.”