Northland's 200 outdoor tsunami sirens will be tested on Sunday, as usual coinciding with the end of daylight saving.
Sirens from Te Hapua to Mangawhai will sound twice, for 10 minutes at 10am and again for 30 seconds at 10.30am, and will be monitored for any faults.
Victoria Harwood, spokeswoman for the Northland Civil Defence Emergency Management Group, said Northland already had more tsunami sirens than any other region of New Zealand, and there was an ongoing programme to expand the network.
Twelve new sirens had been installed recently in the Whangarei district.
Plug-in indoor sirens were also for sale for anyone who lived in tsunami evacuation zones but, for whatever reason, was unable to hear their nearest outdoor siren. Those units were tested at the same time as the outdoor versions.
Harwood said siren testing was an opportunity for Northland residents and visitors to find out if they lived, worked or played in a tsunami evacuation zone, and to plan their evacuation route by checking out the Northland tsunami evacuation maps (at nrc.govt.nz/evacuationzones).
She also advised people to familiarise themselves with the risk of local-source tsunami (those generated on or close to the coast), which could arrive ahead of any official warning.
"Everyone who spends time on the coast needs to know the natural warning signs of tsunami — a strong earthquake that is hard to stand up in or one that lasts longer than a minute, or out-of-the ordinary sea behaviour, such as a sudden rise or fall and/or unusual noise," she said.