More than 200 tsunami sirens across Northland will be tested on Sunday morning to make sure they are working as intended.
The first test will take place at 10am and last 10 minutes, with the second at 10.30am for 30 seconds.
The region's extensive tsunami siren network stretches from Te Hāpua, near Cape Rēinga in the north, to Mangawhai in the south and Ruawai in the west.
Northland Civil Defence spokesman Zach Woods said new sirens were currently being installed around the region, but only the existing network would be tested on Sunday.
The twice-yearly siren tests were timed to coincide with changes in daylight saving time.
Woods said it was important Northlanders also recognised nature's tsunami warning signs.
"Local source tsunami - those generated close to the coast - can arrive ahead of any official warning, so everyone who spends time on the coast should know the natural warning signs of a tsunami.
"They are a strong earthquake that's hard to stand up in or one that lasts longer than a minute, or unusual sea behaviour, such as a sudden rise or fall, or unusual noise."
Woods said the old sirens would continue to be used and maintained until all the new sirens were operational. Only then would the old ones be removed.
He said Northlanders could also use [www.nrc.govt.nz/evacuationzones Northland Civil Defence's interactive maps] to plan their quickest route to safety in the event of a tsunami.
Northland's outdoor tsunami sirens are funded and owned by the Far North District, Whangārei District, Kaipara District, and Northland Regional councils.