Heavy rain is expected to settle in over the top of the country today.
A low was predicted to bring downpours and isolated thunderstorms for Northland and parts of Auckland, WeatherWatch.co.nz analyst Philip Duncan said.
"Yet again Northlanders have a wet nor'easter today with isolated areas of torrential rain moving south this afternoon."
While heavy rain would not be widespread, the areas that would bear the brunt of the rain could see localised surface and flash flooding, Mr Duncan said.
Motorists were advised to drive with care, especially those heading out of Auckland for the weekend later today, and motorists in Northland across today.
Heavy rain was likely to move across Auckland later today, but it would not linger, he said.
"For Auckland rain will most likely clear by midnight."
Tonight the pockets of heavy rain would hit Bay of Plenty and East Cape, Mr Duncan said.
On Saturday a humid northerly flow should produce scattered thunderstorms across parts of the upper North Island, mainly north of Taupo.
Cooler sou'westers were forecast to move in on Sunday with heavy showers clearing by dawn, he said.
MetService said most of the country would get a drenching over the weekend.
"We're expecting that very few places will miss out on rain," MetService meteorologist Peter Little said.
"The heaviest and most persistent falls are expected in the north and west of both islands, and a heavy rain watch has been issued for some regions."
It was good news for farmers on the West Coast, where a near-record dry spell should come to an end, he said.
"It's not often that folk on the coast want rain, but after three weeks of unseasonably dry weather this rain will be welcomed by many."
As the trough crosses the country the moist northerly flow would be replaced by cooler southwesterlies.
"By the end of the weekend the rain should have cleared as a ridge builds behind the trough, though a few showers will linger in the west," Mr Little said.
"However, another rain bearing trough is readying itself to move onto the country early next week, so the more unsettled weather pattern we expect during springtime looks to have finally arrived."
