Mountain Safety Council CEO Mike Daisley said people should use common sense.
"This is a good time for folks to stay inside the ski-area boundaries, where the snow-safety teams are actively managing the terrain."
While the northwest flow would fall as snow at upper levels, in other areas it would bump up the winter temperatures and also bring some heavy downpours.
Christchurch was forecast to hit 19C tomorrow.
The North Island is set to escape the worst of the wet weather today and tomorrow, before it kicks in late Sunday.
A ridge of high pressure sitting over the North Island was keeping the weather relatively settled today, MetService meteorologist Bill Singh said.
It was a cold start in some places, with the lowest temperature -4.2C in Waiouru and the Desert Rd. There were also frosts in central and eastern areas.
Auckland and Whangārei were in for a warm winter day with light winds and a high of 15C.
Most northern spots were in for a similar day, with temperatures in the mid teens.
However, it was a wetter story in the south.
A moist northwest flow was covering the lower South Island, and a series of fronts were passing over the region through tonight, before a more active front arrived Saturday.
Severe weather warnings were in place in Westland and Fiordland to Saturday morning, with up to 350mm rain forecast in some places.
The active front would move over the South Island Saturday, bringing rain and showers to most areas, before arriving in the North Island with showers late in the day.
Auckland, Northland, Gisborne and the east coast would be sheltered from the initial effects, however showers were forecast Saturday through Wellington, Taranaki, Waikato and Bay of Plenty.
These showers would turn to rain Sunday, and start to hit the upper North Island by the evening.
"As the trough moves north late Sunday there will be a boost of heavy rain," Singh said.
In Auckland and Northland there could be heavy falls Sunday night into Monday.
"The front will be followed by an unstable westerly flow, so a showery start to next week," Singh said.
Today's weather
Whangārei
Cloudy periods, chance shower. Light winds. 15C high, 6C overnight.
Auckland
Fine. Light winds. 15C high, 7C overnight.
Hamilton
Fine, apart from morning frosts or fog. Light winds. 13C high, 1C overnight.
Tauranga
Fine with light winds. 14C high, 5C overnight.
New Plymouth A fine morning, then cloud and northwesterlies from afternoon. 14C high, 9C overnight.
Napier Fine, morning frosts. Light winds. 14C high, 4C overnight.
Wellington Mainly fine, clouding up towards evening. Northwesterlies picking up. 13C high, 11C overnight.
Nelson A fine day, then becoming cloudy in the evening. Northerlies developing morning. 14C high, 5C overnight.
Christchurch Thick high cloud. Northerlies. 14C high, 6C overnight.
Dunedin Thick high cloud, with light rain from afternoon. Northerlies gradually strengthening. 13C high, 9C overnight.
