"If your phone is capable of receiving emergency mobile alerts, the alert should appear automatically on your phone's screen with a unique and penetrating warning sound. As it is about keeping you safe, you won't be able to opt out of receiving it," Mr Edwards said.
"It is expected around one third of phones will initially be able to receive the alerts. This number is expected to rise substantially over time as people replace their phones with newer models."
Mr Edwards says because the Whanganui District is at risk from several emergency event scenarios such as floods, extreme weather, earthquakes, tsunami and volcanic eruptions, the emergency mobile alert is another way people can be effectively warned and quickly find out what to do when there is an emergency.
You can check whether your phone will receive the alert and find out more at civildefence.govt.nz.
