Emergency services are responding to reports of flooding in Auckland as heavy downpours hit the city.
An active front is moving over the North Island today with a moderate risk of thunderstorms producing severe localised downpours.
Fire and Emergency New Zealand is starting to get weather-related callouts as the active front marches down the country, with a heavy-rain "watch" also in place for the Bay of Plenty and Rotorua.
Fenz northern communications said they were responding to two flooding callouts in Auckland.
One was at a residential property in Titirangi, and another at a commercial property in Grey Lynn.
A spokeswoman for Bunnings Warehouse Grey Lynn has confirmed there had been flooding in the store but were unsure of the damage as they were still assessing the situation.
The store was operating as normal, a spokeswoman said.
In the South Island, Waimate District Council had issued a flood warning for the Pareora River.
Farmers with stock in low-lying areas were advised to move to higher ground.
"Over the last 24 hours there has been 70mm of rain in the Pareora catchment and there's a possibility for more rain tonight."
Niwa has also reported an active thunderstorm in the Whenuapai area.
WeatherWatch NZ posted a weather alert for Auckland, saying the heavy downpours and thunderstorms this afternoon was creating a risk of flash flooding.
Downpours should ease to showers by late afternoon in Auckland.
The wet weather had meant Auckland's annual Santa Parade was postponed due to the poor conditions.
Organisers confirmed that the parade will be delayed until next Sunday, December 2 due to severe weather warnings.
The parade has not been cancelled since the 1990s, the organisers said.
A heavy rain warning was in place for Wairarapa, Tararua District, Eastern Marlborough and also the sounds until 10pm Monday.
Up to 180mm of rain was expected to hit the ranges and up to 120mm on the coast.
Looking ahead, the complex low-pressure system over New Zealand was forecast to slowly move away to the east on Wednesday.
There was high confidence, 60 per cent chance, that rainfall accumulations would reach warning criteria in Dunedin, North Otago, Canterbury, Marlborough, the eastern hills of Wellington and Wairarapa on Monday.
Elsewhere, MetService forecaster Ravi Kandula said a heavy-rain "watch" was in place from 5am to 5pm today for the Bay of Plenty and Rotorua. A watch is a step short of a warning.
Kandula said that in Bay of Plenty and Rotorua there was the potential for "warning amounts" of rain - 50mm in the 12-hour period - to accumulate.
Heavy-rain watches were also issued for Northland to 9am today; Auckland, Great Barrier Island and Coromandel Peninsula to 1am; eastern Marlborough to 9pm tomorrow; Canterbury plains and high country and North Otago to 6am tomorrow.
"Meanwhile, the confidence for warning amounts of rain about the northwestern ranges of Nelson and Mount Taranaki is moderate on Monday," MetService said.
"On Wednesday and early Thursday, there is moderate risk of warnable amounts of rain in Hawkes Bay and Gisborne."
On Tuesday, there was a low risk that rainfall would reach warning criteria in Northland, Auckland, Coromandel Peninsula, Waikato, Bay of Plenty and the central North Island high country.