Lightning strikes are lighting up the skies in many areas, with storms and a swathe of yellow and orange weather warnings and watches across much of the motu.
By 7pm, NZTA was warning of surface flooding in Wellington, with drivers asked to take care on SH1in the suburb of Mount Cook and at the Basin Reserve.
MetService said its rain radar was pasted with storm signs, and evidence of lightning strikes was plastering the Transpower lightning strike recording data, across many parts of the lower North Island and top of the South Island.
The heaviest rain is expected in the South Island, while the thunderstorms were expected to move up the North Island during Saturday and into Sunday.
The angry weather will sweep up much of the North Island overnight from midnight Saturday through to 7am Sunday, MetService forecasters say. It could become severe or bring heavy downpours, flash floods and dangerous driving conditions, with wind gusts of up to 110km/h or stronger.
“Some of these thunderstorms may generate localised downpours of 25 to 40 mm an hour, especially from Waitomo southwards,” a MetService spokesperson said.
“Wind gusts of this strength can cause some structural damage, including trees and power lines.”
An orange thunderstorm watch has been placed over: Northland, Auckland, Waikato, Waitomo, Taumarunui, Taupō, Taranaki, Taihape, Wanganui, Manawatū, Tararua, Kāpiti-Horowhenua, Wairarapa and Wellington.
The Tararua Ranges in particular are expected to get a drenching, with an orange heavy rain warning issued, for the period from 6pm Saturday to 6am Sunday.
A yellow heavy rain warning is in place, until 5am Sunday, for: Waikato, Taupō, northern Taranaki and northern Taihape.
A yellow heavy rain warning is in place, until noon Sunday, for: parts of the Bay of Plenty and Gisborne-Tairāwhiti.
A strong wind watch has been added for Northland, Auckland and Manawatū, on top of the earlier strong wind watches in place for: parts of Waikato, Taupō, Taranaki, Taihape and Whanganui, and for Wellington and Kāpiti Coast.
South Island squalls
The west of the South Island is expected to cop the heaviest dumpings of rain for the country this weekend, along with the headwaters of the lakes and rivers of Otago and Canterbury, MetService forecasters said.
Meanwhile, strong winds will buffet many parts of the mainland.
The Transport Agency said it plans to close part of State Highway 94 road from Te Anau to Milford Sound from 10am Sunday, ue to the forecast, with the weather elevating the risk of avalanches.
New yellow heavy rain watches were issued during Saturday for parts of Tasman, Nelson and Marlborough, the Grey and Buller districts, into the early hours of Sunday.
Orange heavy rain warnings are in place for parts of Westland and parts of Canterbury, where there could be up to 140mm rain on top of what has already fallen.
The same areas should expect snow down to about 1800m.
An orange wind warning was in place for the Canterbury High Country into early afternoon Saturday, where severe northwesterly gales were expected, gusting to 120km/h.
Yellow strong wind watches, approaching severe gales, are in place for: the Tasman District and Marlborough Sounds.
And forecasters say that while Otago, parts of Southland and Fiordland have been weathering strong winds on Saturday which had eased for the day by early afternoon on Saturday – northwesterly severe gales are expected to be back from Sunday afternoon.
