Millions of Brits' phones will vibrate and make a siren sound for around 10 seconds as they receive a text of fewer than 100 words at around 3pm on the day.

Alerts may be sounded because of severe flooding, fires and extreme weather

Message will be sent to millions of phones on Sept 7 at 3pm as part of the UK’s alert system

Millions of Brits' phones will vibrate and make a siren sound for around 10 seconds as they receive a text of fewer than 100 words at around 3pm on the day.