Demand for electricity rose to a record high this week as Kiwis reached for their heater dials to stave off the cold.
Airports and schools were closed yesterday as the bitter polar blast battered the country.
Entire towns were cut off when roads were closed, and emergency services were kept busy with weather-related incidents.
Food ran out in some places, sports fixtures were cancelled and black ice and heavy snow made driving treacherous.
Snow fell briefly in Northland, dusting Dargaville, the outskirts of Whangarei and the top of the Tutamoe Range in north Kaipara.
Last night, the lower North Island was feeling the full force of the wintry blast, with heavy snow returning to Wellington.
Snow was expected to fall to sea level, or low levels in the capital during the night, WeatherWatch analyst Philip Duncan said.
"Snow is expected to be heavy around Wellington, Upper Hutt and Wairarapa."
Transpower said the demand for electricity reached a record high, causing stress to the national power grid and "dips" in some areas.
It said the extreme weather led to a peak demand figure of 7048MW at 6pm on Monday - 120MW higher than the previous high, on July 25.
Demand rose a further 50MW about 7.30am yesterday.
Transpower chief executive Patrick Strange said the grid was being monitored and crews were on standby in case anything went wrong.
"Having snow, ice and lightning across the country for several days is a once-in-a-generation event and I suspect it will keep us busy over the next few days. If we lose power to areas, we'll do our best to keep it short."
St John Ambulance was also busy tending to people who injured themselves while walking to work on icy terrain.
And police warned drivers in Canterbury, Otago, Southland and Wellington to stay off the road unless travel was essential.
Several roads were closed in the Wellington area last night and Inspector Ken Climo, from the Central Communications Centre, said extreme caution was needed.
"If you need to make essential travel this evening, make sure you are equipped with food, warm clothing and blankets for all occupants, in case you cannot return to your destination this evening."
Canterbury road policing manager Inspector Al Stewart said roads in the district were expected to freeze overnight, making them even icier.
"Even without fresh snow on the roads, drivers need to be aware of the dangers of ice, especially black ice which you can't see."
Further south, essential supplies began to dwindle in Queenstown, with roads in and out of the town and airport closed for a large part of the day.
Bakers were making extra bread to supply supermarkets, but other necessities including fuel and milk were running low.
Retailers were also gearing up.
- Additional reporting: NZPA