A meteorologist is warning Wellington could face "major impacts" if hit by an approaching low-pressure system bringing heavy rain.
MetService is forecasting another drenching for northwestern parts of the South Island and the lower North Island on the back of two very wet days for those areas.
The wet weather comes from a low over the north Tasman Sea which is expected to deepen and approach central New Zealand on Friday.
Severe gales in parts of New Zealand from Taranaki down to Westland are possible.
MetService said there is still uncertainty surrounding the details of where the heaviest rain around the upper South Island and lower North Island will fall
"Depending on the exact path of the low-pressure centre, there could be major impacts for Wellington, and the area is likely to be upgraded to an Orange Heavy Rain Warning," MetService meteorologist Dan Corrigan said in a statement.
"Even if warning criteria is not reached, there is still a risk of impacts like surface flooding, slips, and rising rivers in already sodden areas. These hazards, along with poor visibility in heavy rain, can also cause travel delays and disruptions."
Otago and Southland will be the only regions to avoid the rain with the low, and as it moves away during Saturday and overnight into Sunday, the settled weather will spread to the rest of New Zealand.
MetService has issued an orange heavy rain warning for Westland between Otira and Bruce Bay from 10pm Thursday until 8pm Friday with up to 110mm of rainfall possible.
Orange heavy rain warnings have also been issued for Mount Taranaki and Tasman west of Motueka on Friday through until Saturday morning/noon.
A heavy rain watch has also been issued for Friday in Wellington, Kapiti Coast, Wairarapa south of Greytown, and the Tararua Range, Buller, Westland north of Otira, and the remainder of Nelson/Tasman not under orange warning and the Richmond and Bryant Range, including the Rai Valley and the Marlborough Sounds.
Additionally, a strong wind watch has been issued for Taranaki about and south of the mountain, Taihape, and Whanganui north of the City from Friday evening until Saturday morning.
On Sunday afternoon, MetService said a change to strong, cold southwesterly winds will arrive in the deep south, bringing showery weather there with a dusting of autumn snow on the mountains above around 800m.
The cooler temperatures and showers will spread northwards across the rest of the country on Sunday night while blustery southwesterly winds affect exposed coastlines. However, the showery weather is expected to become confined to the east coasts on Monday, with plenty of sunny skies opening up across the country, MetService said.
"Looking ahead to ANZAC day, we have reasonable confidence at this stage that high pressure will bring settled weather for most of the South Island, but it could well be a frosty one for people waking up early. Southwesterly winds may still be quite breezy in the North Island, but the weather looks largely dry aside from showers for eastern parts," Corrigan said.
MetService's extended forecast:
Saturday
North Island: Periods of rain, with heavy falls possible from Taranaki to Wellington, easing in the west and south later.
South Island: Rain in the north, with heavy falls possible, easing to isolated showers. Partly cloudy elsewhere, but showers over Fiordland and the south coast.
Sunday
North Island: Scattered showers in the east and north. Partly cloudy elsewhere, with isolated showers late.
South Island: Rain developing in the west. Partly cloudy in the east, with showers developing south of Christchurch. Strong southwesterlies developing, gale about the southern coast.
Monday
North Island: Scattered showers.
South Island: Rain in the west clearing. Showers elsewhere, easing or clearing inland later.
Chatham Islands
A few showers turning to rain later Saturday, some possibly heavy, and northwesterlies becoming strong. Rain clearing to partly cloudy on Sunday as winds turn lighter southwest. Showers with strong southwesterlies on Monday.
