The polar surge in the capital forced police to close roads, including the Rimutaka Hill Road, Wainuiomata Hill Road, Paekakariki Hill Road, and State
Highway 58 between State Highway 2 to Moonshine Road and Blue Mountains Road in Upper Hutt.
Police said driving conditions were treacherous and people should only travel if it was essential.
Extreme caution was needed on all roads in and around the Hutt Valley.
Snow was expected to fall to sea level, or low levels in Wellington until midnight, WeatherWatch analyst Philip Duncan said.
"Snow is expected to be heavy around Wellington, Upper Hutt and Wairarapa tonight with a moderate risk of snow flakes returning to low levels of the lower North Island like Wanganui and Taranaki''.
MetService spokesman Bob McDavitt said strong southerlies were bringing severe wind chill to coastal areas between Canterbury, Wellington and Wairarapa, but should gradually ease later tomorrow.
Snow in Christchurch was not expected to be as heavy as it was yesterday, WeatherWatch analyst Richard Green said.
"The freezing level has lifted just enough so that Christchurch, Timaru and Ashburton are all on the borderline of snow. It's an extremely fine line between sleet, rain and snow for those centres tonight but we don't expect the falls to be as long lasting and heavy as they were last night.''
A few brief snow flurries were possible in Dunedin, but conditions were easing.
St John South Island regional operations manager Chris Haines said 111 should only be called in an emergency because each callout was taking longer with the weather conditions.
"Our ambulance officers have been to some incidents where it turned out that people didn't need an ambulance.
"We're talking about instances where people have called an ambulance for a toothache, or a sore throat, or a bleeding nose.
"It's important that we utilise our resources appropriately, and keep them available for genuine emergency situations.''
More than 20,000 homes in the lower North Island had lost power at one time or another since Sunday, Powerco network coordination manager Dean Stevenson said.
About 300 properties currently remained without power, mainly in south Taranaki, and rural Wanganui, Manawatu and Wairarapa.
"We have had more damage today in areas including New Plymouth, Waverley, Linton and Eketahuna so repairs are continuing but we are still sustaining damage. While we are making good progress it is clear some customers will be without power again tonight.''
About 400 customers in the Leeston, Southbridge and Brookside areas in Christchurch remain without power, lines company Orion said.
Most bus services in Wellington have been disrupted or cancelled tonight.
Meanwhile, Prime Minister John Key said he expected employers to take "a generous view" toward staff who were unable to make it into work because of problems caused by the weather.
"For the most part, most employees are hard working, they try and turn up to work when they can. I'm sure for the vast bulk they actually will,"he said.
"But if there's a whole lot of snow and ice and you can't get out of your driveway, then you'd expect employers to take a generous view towards that," he said.
Mr Key's call followed claims some employers were threatening not to pay workers who failed to arrive at work.
Police were continuing to warn that roads in many areas remained treacherous as snow became black ice.
"Adjust your speed and following distances accordingly, and take note of any reduced speed limits throughout the region," said Sergeant Peter Theobald, of police central communications.
Police dealt with a series of minor crashes during the morning, but no serious injuries were reported.
Many state highways remain closed, including the Desert Road and the Rimutaka Hill road in the North Island and the Lewis Pass and Arthur's Pass in the South Island.
St John South Island regional operations manager Chris Haines said 111 should only be called in an emergency because each callout was taking longer with the weather conditions.
"Our ambulance officers have been to some incidents where it turned out that people didn't need an ambulance.
"We're talking about instances where people have called an ambulance for a toothache, or a sore throat, or a bleeding nose.
"It's important that we utilise our resources appropriately, and keep them available for genuine emergency situations."
More than 20,000 homes in the lower North Island had lost power at one time or another since Sunday, Powerco network coordination manager Dean Stevenson said.
About 300 properties currently remained without power, mainly in South Taranaki, and rural Wanganui, Manawatu and Wairarapa.
"We have had more damage today in areas including New Plymouth, Waverley, Linton and Eketahuna so repairs are continuing but we are still sustaining damage. While we are making good progress it is clear some customers will be without power again tonight."
About 1000 customers in rural central Canterbury, in areas including Rakaia, West Melton, Leeston and Greendale were without power overnight.
Electricity network Orion general manager commercial Rob Jamieson said the company was expecting to make real progress reconnecting the majority of affected customers from early this afternoon.
The Ministry of Education said it was up to individual schools to decide whether to open today, and a number in Wellington's western and hill suburbs opted to close.
Freezing conditions have also made it especially hard for homeless people to cope.
Wellington night shelter manager Mike Leon said demand for a warm bed jumped 50 percent last night.
Airports in Christchurch and Queenstown reopened this morning, and some flights were operating out of Dunedin.
