More than 5 million mobile phones are expected to receive an emergency alert test tonight.
The Emergency Mobile Alert will go out between 6pm and 7pm on Sunday.
Civil Defence Emergency Management Director Gary Knowles said the alerts were to warn people of threats to life, health or property.
"The nationwide test is a way to check our systems, the cell towers and your phone's ability to receive an Emergency Mobile Alert, so we have confidence it will perform as it should in an emergency."
He said the 2021 disaster preparedness survey suggested 90 percent of people would receive the alert, or be near someone who does.
In a real emergency, information would also go out on radio, television, online and via social media.
There is no need to register or download an app - the alert will be sent to all phones that are turned on and within mobile coverage.
Though the National Emergency Management Agency does advise making sure your phone's operating system is up to date.
It is not possible to opt out of receiving the alert.
"No form of technology is completely failsafe, so it doesn't replace other alerting channels such as radio or social media, or the need to act upon natural warning signs. If you feel your life is in danger, don't wait for an official warning.
"Remember - if an earthquake is long or strong, get gone," Knowles said.