"Snow is most likely in Southland, Otago and Central Plateau over the next 36 hours.
"This cold blast, which started on Tuesday night will finally ease on Sunday."
Following the wet and snowy weather falling tonight and Saturday morning, it will significantly increase the chances of black ice, mostly on South Island roads and highways, according to RuralWeather.co.nz.
Central Otago and northern Southland will also be bitterly cold with overnight lows down to -4C to -6C while places like Queenstown to Arrowtown will drop to -2 to -4C in some locations.
"The North Island's Central Plateau will be the coldest in the north with overnight lows around Waiouru, Ohakune and National Park getting down to -4C next week.
"But nearby Taupo and Rotorua are more likely to be caught up in the airflow of the northern low pressure system. Overnight lows for those two main centres gets down to about +2C to -1C," a spokesperson said.
RuralWeather.co.nz is forecasting overnight lows to dramatically drop in the South Island from Sunday night with lows of -7C to -12C in the high country.
"Places like Tekapo and Twizel and surrounding areas are most exposed to this extreme cold.
"Following the wet/snowy weather falling again tonight and Saturday morning it will significantly increase the chances of black ice, mostly on South Island roads and highways."
The cold air then moves up the South Island with snow flurries in the mountains and ranges as it heads towards the North Island, WeatherWatch.co.nz is forecasting.
"The low doesn't look too serious but with the incoming high it will generate some windy 'squash zone' weather and the consistent easterly flow will see rain accumulating in the north and east.
"This is good news for dry parts of the Far North and Northland which may get 30mm to 50mm of rain but it will come with winds gusting into gale-force for some, up to 80km/h in some exposed places."