A cold snap could bring snow to the east coast and rain to the already sodden top half of the country, forecasters warn.
But the chilly weather was good news for skiers, as low pressure systems were expected to bring a dump of snow to the South Island, MetService said.
A severe weather watch was in place for the ranges near Gisborne and Hawkes Bay north of Wairoa, meteorologist Liz Walsh said.
"There's snow to 800m, which is quite low for the North Island - but it's unlikely to affect any roads, basically because there's none through there."
The worst of the weather would strike at the weekend, she said.
The country would be sandwiched between two areas of low pressure to the east and west, which were set to come together.
"The low pressure up north is going to cross over the upper North Island over Saturday and Sunday, so we're expecting heavy rain for Auckland and the Coromandel on Saturday and western parts of the Bay of Plenty and the Kaimai [Ranges] and Gisborne on Sunday," Ms Walsh said.
Meanwhile a severe weather watch had been issued for Northland.
"We do think the heavier rain will fall further south, but any rainfall in Northland will doubtless affect conditions up there, so we're very wary of what we're forecasting there and keeping a close eye on it."
Weatherwatch.co.nz weather analyst Philip Duncan said latest data suggested the rain band in Northland could be "fairly fast moving".
"We'd be concerned with any dramatic torrential downpours or hours of moderate rainfall -- at the moment neither of those are looking too likely."
Ms Walsh said further south, Canterbury would be the first to feel the southerlies and showers tomorrow, which would move up the country and reach the North Island on Sunday.
"There could even be snow down to 400m in the Canterbury Plains."
Snow was predicted to reach lower levels on Sunday at Dunedin, Southland and Clutha.
"We're heading into the coldest time of the year," Ms Walsh said.
Northland Civil Defence said the severe weather watch issued for the area over the weekend reflected a "sensible, cautious approach" and was no cause for alarm at this stage.
"Forecasters will continue to monitor the situation, and their advice -- which we agree with -- is that people should keep up to date with the latest forecasts as they come to hand in case the watch is upgraded to a full warning," Civil Defence spokesman Tony Phipps said.
Local officials, including hydrologists and other experts, were also monitoring the forecast progress carefully.
Northland's post-storm recovery efforts, now into a sixth day, continued to progress well, he said.
The reopening of a crucial section of State Highway 1 affected by a huge slip south of Kawakawa was expected late tomorrow or early Saturday.
New Zealand Transport Agency said getting SH1 partially opened depended on the good weather holding.
"But our contractors are making great progress constructing a detour past the underslip that forced us to close the highway," regional journey manager Jacqui Hori-Hoult said.
Main road closures around the country:
* SH1 between Kawakawa & Towai. Road closed due to a slip;
* SH12 Kaikohe to Dargaville. One lane open.
* SH3 south of Te Kuiti and north of Waitara. One lane open due to rock falls.