It was revealed on Friday night Auckland would enter a state of emergency for at least a week after torrential rain and flash floods punished the region.
States of emergency have been declared dozens of times since the legislation was enshrined in the Civil Defence Emergency Management (CDEM) Act 2002 - most notably in response to extreme weather events and when New Zealand first entered COVID-19 alert level 4 in 2020.
Civil Defence says a state of local emergency gives powers to authorities that would otherwise not be available.
"Some emergencies need extra coordination across services," CDEM says. "In this case, a state of local emergency can be declared.
"A state of local emergency gives the relevant CDEM group special powers to deal with the emergency."
In short, the state of local emergency in Auckland will give the supercity's CDEM group the powers to coordinate other emergency services, make sure temporary accommodation, food and water are available, ensure access to dangerous areas is properly controlled and provide regular public information meetings.
"This declaration reflects the extent of damage, displacement and disruption caused by this evening's severe weather event and enables emergency services and response agencies to draw on resources, and enact additional powers, to assist affected Aucklanders," Mayor Wayne Brown said after declaring the state of emergency overnight.
"We want to make sure that all residents are kept informed, and emergency services are able to reach those who are most vulnerable and at risk as quickly as possible. Do not put yourself at risk."
At a press conference overnight, CDEM Minister Kieran McAnulty said the National Emergency Management Agency was able to bring in additional resources after the state of emergency was declared - including setting up a "bunker" at Parliament to provide support with communications.
So far, "dozens" of people have attended evacuation centres throughout Auckland, he told Newstalk ZB on Saturday morning. However, he believed the total number of people evacuated overnight would be "significantly higher".