A nationwide test of the emergency mobile alert system will take place later this month.
The alert will be sent out to mobile phones between 6pm and 7pm on Sunday, 25 November.
Civil Defence said it expected about half of all mobile phones would received the alert.
A similar test held last November reached about a third of all mobile phones.
Ministry of Civil Defence and Emergency Management director Sarah Stuart-Black said the annual test of the system helped to ensure it was working effectively, while also helping to familiarise the public with what to expect and how it worked.
"By running this test and asking people to be aware of the alerts, we are able to test our systems, the cell towers and your phone's ability to receive an Emergency Mobile Alert," Mrs Stuart-Black said.
"This is just a test, but when emergencies happen, Emergency Mobile Alert will be a vital channel to help keep our communities safe.
"Not all phones are currently capable of receiving the alerts, so we need people to look after each other: if you receive an alert, tell your neighbours, your whanau, your colleagues."
The system can geographically target areas and it did not get affected by network congestion.
"Last year's nationwide test was not only invaluable in spreading awareness of the system, but also in highlighting issues with some handsets, so we could work through them with the manufacturers," Ms Stuart-Black said.
The test alert message will contain a link to the Civil Defence website, where recipients will be able to fill in a survey that will help to inform further improvements to the system.
Find out more about Emergency Mobile Alerts, including whether your mobile phone was compatible, at the Civil Defence website.