Emergency alerts will be sent to all UK mobile phones next Sunday (23 April).
A message will appear on the screen during the test, and the phone will vibrate and users will hear a loud warning sound for 10 seconds, even if the phone is set to silent.
Users will have to acknowledge the alert before other features become operational on their devices.
Users can opt out by searching the device settings for emergency alerts and then turning off severe and extreme ones.
Government officials say however the alerts could be life-saving and advises against switching them off.
Messages would only ever come from the government or emergency services and will initially focus on the most serious weather-related events.
