Explainer: How emergency alerts work and why you'll get one on Sunday

Explainer: Looking forward to a quiet Sunday night? Your phone may have other plans.

The annual test of the country's emergency mobile alert system will be between 6 and 7pm on Sunday.

But don't panic, even if the buzzing gives you a start.

"(People) do not need to act, other than check that they've received it," National Emergency Management Agency (NEMA) communications manager Anthony Frith said.

What are these emergency alerts of which you speak?

The warning broadcast to your mobile phone sends out a loud buzz along with a text of important information. They'll come in even if your phone is on silent mode, in a cinema or at a concert.

We first started hearing them in 2018 and they became quite familiar during the Covid-19 pandemic. They've been used for everything from cyclones to forest fires, boil water notices and chemical leaks.

"The EMA is a really important tool in helping keep Kiwis safe," said Telecommunications Forum Chief Executive Paul Brislen. "With increasing number of events, and events becoming more severe, it's vital we give people as much notification and warning as we can."

An annual test of the alerts comes each year.

"The test gives us confidence that the system is working as it should, across the whole country," Frith said.

"It's also a chance for people to familiarise themselves with how the alert sounds and displays on their phone, so they recognise it in a real emergency."

NEMA said that their 2025 emergency preparedness survey showed that 92 percent of people received the test or were with someone who did.

The test will also have a link to NEMA's website, where people can fill out a survey about their experience.

What's it sound like again? Here's a reminder:

Are we getting more of these alerts lately or is just me?

It's not your imagination - there are more emergencies than ever.

"Over the last 12 months, 66 alerts have been issued, compared to 53 in the same time period previously," Frith said.

"This primarily reflects the severity and frequency of severe weather events that we've seen over this time, noting also that alerts have been sent for other reasons too."

Brislen said New Zealand is ahead of our rival across the ditch when it comes to emergency notifications.

"It's worth noting Australia is only just trialling their equivalent: we're well ahead on that note."

There are sometimes complaints that alerts don't always result in big disasters, such as the state of emergency declared and evacuations over huge waves in Wellington coastal areas earlier this week that turned out to be less dramatic than expected.

Some Wellingtonians also reported to RNZ that they didn't receive alerts right away on Monday or saw long delays.

There were also problems reported last July when a massive 8.8 magnitude earthquake in Kamchatka off the coast of Russia triggered a tsunami warning. Many New Zealanders got a 6.30am alert, but some didn't at all, while others got it multiple times in what NEMA Civil Defence Emergency Management director John Price called a glitch.

Frith said the system actually worked well during the Kamchatka incident, but there were issues at the receiver end.

"It's not surprising that a variety of issues will arise when sending an alert to around 3.5m phones."

Some reported problems with alerts aren't actually problems at all or result from not understanding where a specific alert is targeted for. Last year a Hamilton family told RNZ's Checkpoint they didn't get an alert over the potential tsunami - but Frith noted they weren't supposed to get one.

"The reason they didn't get it is because Hamilton is obviously not at risk of tsunamis.

"We're working really hard to educate the public to ensure people understand how the system works, that we only send alerts to areas impacted, and what might cause perceived issues."

In regards to Monday's alert in Wellington, there were no issues with the EMA system, Frith said.

"There can be a number of reasons why people don't receive an alert. However, factors like the location, movement of people and network conditions can all affect when a device displays the alert."

How can they send messages to millions of phone, anyway? Is it witchcraft?

Alerts use cell broadcast technology known as geotargeting to send alerts through cell towers in a selected area - which can be the entire country, as in Sunday's test, or down to a small section of a city.

New Zealand's system was provided by a division of Everbridge Public Warning, an American software company that specialises in alert systems. Everbridge says of their tech that "one message can be sent to millions of devices within a target area in seconds".

When an alert is issued, the agency involved will select how big a region is covered, depending on the specific crisis.

"The operator who sends the emergency alert will draw a polygon around that area, a shape they need to make sure is big enough to capture cell phone towers in the perimeter," Frith said.

Auckland Emergency Management general manager Adam Maggs previously told RNZ that while targeted messages work well, who gets them varies, depending on a variety of factors.

"In terms of one person [in a household] receiving a message and another not, this could be due to being just outside of the geographically targeted area. The boundary for the geotargeted area is not a 'hard' boundary and there can be message leakage, depending on the location of cell towers.

"Other reasons include having a phone that may be older or has missed a software update, or the phone may not have had mobile reception."

Frith said that ongoing improvements in mobile coverage help increase alert efficiency.

"Network operators are constantly enhancing coverage, capacity, and performance as they roll out new infrastructure and technologies like 5G. That in turn can improve how consistently alerts are received."

Wait, does this mean they've got my phone number?

Not at all.

The system uses the cellphone network as a carrier of the notifications that NEMA or other emergency agencies send out.

"A really oversimplified way of putting it, it's like a signal that your phone picks up, which is almost like radio," Frith said.

"Our system does not have any telephone numbers. Once we've transmitted the message from our portal, it then goes to the cell towers."

Who decides when the alerts go out?

Only certain agencies have the power to send out alerts - NEMA, Civil Defence Emergency Management groups, NZ Police, Fire and Emergency New Zealand, the Ministry of Health and the Ministry for Primary Industries.

There's a protocol in place around how alerts are sent, based on certainty, severity and urgency and typically requiring multiple people to sign off on them.

One big message that NEMA is putting out there is that emergency alerts are only part of disaster preparedness.

"We encourage people to get their information from multiple official sources, as we don't want people relying on EMA as their sole source of emergency information." Frith said.

"People need to understand that the warning is the last line of defence and if they're concerned at all but haven't got the alert yet not to wait - get clear of the situation if they can," Brislen said.

NEMA encourages following MetService warnings, local Civil Defence groups on social media and radio news such as RNZ, New Zealand's statutory civil defence lifeline radio broadcaster.

"Often the best alert comes from nature itself - so remember to use your danger sense and act immediately if you experience the natural warning signs" like rising floodwaters, an earthquake or indications of a landslide, Frith said.

Officials are aware of the potential for overdoing alerts, he said.

"Emergency alerts are issued only when there is a severe and urgent threat to life, health or property. The reason they're used so sparingly is to ensure people don't develop alert fatigue, or start to ignore them."

Look, I'll be taking a nap on Sunday. Can't I opt out of the test?

Sorry. There's no way to choose not to get an emergency alert, and because it's broadcast from cell phone towers, there's no "list" of names to be removed from.

If you don't want to be alarmed by Sunday's test, the only real option is to switch your phone to airplane mode or turn it off entirely.

"The feedback I hear is that people don't like the alerts but value them hugely," Brislen said.

"They're loud, disruptive and don't always all arrive at the same time for all household members. But people do value the alerts and treat them seriously, which is the key."

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