The Antarctic blast, described by MetService as close to a one in 50 year event, has seen roads, schools and airports closed, cut power to thousands of homes and stopped mail deliveries in parts of the country.
The storm had also brought snow in places that don't usually see it, including Wellington and Auckland where snow hasn't fallen in more than 30 years.
MetService spokesman Bob McDavitt said today was likely to be the coldest day and warned New Zealanders to prepare for more snow over the next few days.
"Snow is expected to move offshore during Wednesday," he said.
"As the clouds move away and the winds die down, you'll have frost and black ice on Thursday, maybe even moving into Thursday night or Friday in the central areas."
The heaviest snowfall was expected between Canterbury and Wairarapa, as well as Manawatu towards Taranaki.
"The conditions are cold enough to bring snow down to 300 metres, the height of the Sky Tower," McDavitt said.
St John regional operations manager for the South Island, Chris Haines, said people should make sure they have stockpiled enough emergency food, water and other essential supplies as a precaution.
While in Wellington, Civil Defence manager Rian Van Schalkwyk warned residents to stock up on supplies, in preparation for being trapped indoors.
"People should prepare for the worst, which means making sure they're ready in the event that they cannot leave home and may be without electricity and other amenities," he said.
Police have warned of treacherous driving conditions as the snow that blanketed New Zealand today will turn to ice.
Many state highways around New Zealand were closed, including the Desert Road and Rimutaka Hill road in the North Island and the Lewis Pass and Arthurs Pass in the South Island.
"We're warning drivers that, unlike today where the snow was a clearly visible hazard, there will be large areas of ice on the roads tomorrow, especially in rural and shaded areas, that you will not be able to see," Inspector Al Stewart, of Christchurch police, said.
Road users should assess their local road conditions and stay home or delay non-essential travel where possible, he said.
Today, flurries were reported in Clevedon, Flat Bush, Pukekohe and the Waitakeres, while strong winds brought down dozens of trees, toppled power lines and flipped trampolines in south Auckland.
Five people were taken to hospital with moderate injuries in Auckland. A Pakuranga family of four were taken to Middlemore Hospital after a tree fell on their house this morning, and an elderly man was taken to Auckland City Hospital after being blown over.
In the South Island, St John Ambulance attended to nine people, including three in Christchurch, who fell on ice or snow.
Haines said St John has not been as busy today as they were during the snow last month, but the workload had been steady.
"We will continue to monitor the situation for the rest of the day and overnight. We are still using four wheel drive ambulances, as well as other 4WD vehicles as rapid response vehicles," he said.
Eight motor vehicle crashes have been reported to Christchurch police between 6am and mid-afternoon, mostly of a minor nature with no serious injuries.
In the capital, another flurry of snow fell down to sea level in parts of the city, including Lambton Quay, Cuba St and Parliament. Residents in Newtown, Island Bay, and Newlands all reported further snow falls from around 11am.
MetService said the level of snow that fell in Wellington had not been seen since at least 1970s, and another 5cm was expected over the next 24 hours.
The weather today cut power to thousands of households across the country.
Over 2000 Powerco customers in South Taranaki, Wanganui, Manawatu and Wairarapa, and about 100 Orion customers in Christchurch were still without power this afternoon.
Powerco network operations manager Phil Marsh said power would be restored to about 1500 customers by tonight, but some areas would remain without supply overnight and more power cuts were likely tomorrow.
In Wellington, a power outage around 5.40pm tonight affected about 800 households in the Whitemans Valley and Makara areas.
The capital has also experienced power trouble with "voltage dips" this evening. A Wellington Electricity spokesman said it was caused by a rise in demand.
Mail deliveries were cancelled in Hawke's Bay, Wairarapa, Wellington, Canterbury and Otago.
Air and road travel was also disrupted with many roads in both islands closed this morning and flights out of Christchurch, Queenstown and Dunedin cancelled.
Wellington Airport has temporarily put all its flight on hold while the runway was cleared of excess ice and snow. A spokeswoman said the conditions would be constantly evaluated throughout the night.
Around 150 passengers were stranded at Dunedin Airport overnight, and in Auckland, flights to Queenstown have been cancelled and there were no seats available until Thursday.
In the North Island, snow has closed the Desert Road and the alternative route north, State Highway 4, as well as the Rimutaka Hill Rd in Wellington, and the Napier - Taupo Road (SH5).
In the South Island, SH1 between Kaikoura and Waipara is closed, as is the Lindis Pass (SH8), SH6 between Queenstown and Five Rivers, the Lyttelton Tunnel (SH74) in Christchurch, and the highways north and south from Dunedin.
Police advised people to avoid driving if possible in the worst snow-hit areas and to be cautious.
Meanwhile, about 1900 dairy farms in the South Island are dumping thousands of litres of milk as Fonterra's collection tankers are stranded because of the severe weather conditions.
Fonterra's sustainability teams were in contact with farms who need to dispose of milk, and were liasing with regional councils.
The company was unable to say at this stage how many litres it had lost, or whether it would compensate farmers.
- STUFF, with AUCKLAND NOW, THE DOMINION POST, and NZPA