Heavy rain watches in place around New Zealand. Photo: Unsplash / Erik Witsoe
A number of heavy rain watches and warnings were in place around the motu on Thursday.
MetService said a complex trough would cross much of northern and central New Zealand on Friday and would be preceded by rain and strong northeasterlies for many places.
MetService meteorologist John Law told Morning Report there could be bursts of "fairly intensive" rain accompanying thunderstorms on Thursday evening and into Friday.
"Could be some really intense bursts through there, 20-30ml of rainfall not out of the question as [the thunderstorms] run through."
Huge band of rain set to hit NZ
Law said people should keep a close eye on the weather forecasts.
In Northland, there was a heavy rain watch in place from 1pm Thursday until late on Friday morning.
Heavy rain watches were also in place for the areas around Mt Taranaki and Tāupo.
Auckland had both a heavy rain watch (from 8pm Thursday) and a severe thunderstorm watch (from 10pm) in place.
"Between 10pm tonight and 5am Friday, localised downpours of 25-40mm/h are possible in some parts of the Auckland region (including the islands of the Inner Hauraki Gulf)," MetService said on its site.
"These downpours could occur with or without thunderstorms. Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or valleys, and may also lead to slips. Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."
More heavy rain and thunderstorms are also possible on Friday.
The threat of heavy rain in Bay of Plenty from early Thursday morning until Friday evening prompted an orange warning, with "minimal" chance it would turn red.
In the South Island, an orange heavy rain warning was in place for Tasman, northwest of Motueka, from 6pm Thursday until the same time Friday.
A heavy rain watch was also in place for Fiordland north of Doubtful Sound and the ranges of the Westland District, with a low chance of developing into a warning.
"Expect 120 to 150 mm of rain to accumulate. Peak rates of 15 to 25 mm/h. Minimal chance of upgrading to a Red Warning."
New warning processes
MetService was now working closely with the National Emergency Management Agency to ensure the weather watches and warnings were easy to use. That included a note about whether a warning was likely to be upgraded, he said.
"[This front] takes its time to clear through on Friday, there is some drier weather coming back towards us on Saturday with the worst of the rainfall now looking to be staying off down towards the far southern side of the country.
"It's going to be a one to keep a close eye on but I think the worst of the weather hopefully through Friday and things looking a bit better as we head into the weekend."