Auckland is set to experience one of the wettest 48-hour periods the city has had this year.
Weatherwatch.co.nz analyst Philip Duncan said there weren't many parts of the country that often received set-in rain for more than 24 hours.
Fiordland and the West Coast were no strangers to days of relentless rain but further north, rain tended to move through much faster.
The Southern Alps on the West Coast blocked the rain clouds but in Auckland, the city was surrounded by separate bodies of water, the Tasman Sea and the Pacific Ocean, Duncan said.
"With no tall blocking ranges rain clouds tend to pass through quickly, which is why the almost 24 hours of rain in our largest city is unusual - and why more rain for the next 12 hours or so will make this one of the wettest 48-hour periods the city has had this year as far as total hours with precipitation.