The national system for sending emergency alerts to mobile phones in the UK will be tested again this September, the government has said. It will see compatible phones vibrate and make a siren sound for 10 seconds while displaying a message at 15:00 BST on 7 September, even if they are set to silent.

The emergency alert system will be tested at around 3pm on September 7, in its second ever nationwide drill. The first time the system was tested was in April 2023, but some mobile phone users warned their devices did not sound, with the problem traced to specific networks.

The UK government will conduct a nationwide Emergency Alerts test in September, 2025. Here’s when, what time and what it says.