The South Island is receiving the worst of the unseasonably cold snap this evening with sleety showers, snow and hail showers in Canterbury, Otago and Southland.
The temperature in Queenstown and Wanaka is expected to fall below zero overnight and MetService is forecasting further snowfalls in Southland and southern parts of Fiordland and Otago, especially Clutha, tomorrow.
Alexandra in Central Otago is currently the coldest place in the country, on just 1.8 degrees Celsius.
MetService duty forecaster Karl Loots said snow down to almost sea level was forecast for Southland, Clutha and Dunedin, and Christchurch's Banks Peninsula could receive snow down to 100m overnight.
Snowfall warnings remained in place for South Island mountain passes.
Callers to Radio New Zealand from Ashburton said it was snowing heavily there on Monday night.
Rain and thunderstorms are likely in north and western regions of the North Island, with a snow warning for the Desert Road.
Mr Loots said Auckland was also in for a cold day tomorrow with showery and strong southwesterly winds gusting at around 100 kilometres an hour.
Dunedin roads closed
Today snow forced the closure of Dunedin's Three Mile Hill Road and the Ross Creek, Brockville and Halfway Bush bus services terminated early due to ice and snow on the roads.
Further south in Te Anau, residents woke to settled snow with about 10 centimetres falling in Fiordland overnight.
Snow ploughs and grit trucks were working to keep the region's roads open but drivers have been warned to carry chains and watch out for ice overnight and first thing in the morning.
Rain and thunderstorms are likely in north and west parts of the North Island and a snowfall warning remains in place for the Desert Road, MetService said.
Queenstown airport managed to re-open earlier this afternoon and clear some of its back-log after snow shut it down earlier today.
A MetService spokesperson said while the snow was early, it was not unusual and warmer weather was expected to return later in the week.
Road alerts were in place on SH1 from Milton to McNab, SH8 from Tarras to Omarama and through the Lindis Pass, with drivers being asked to drive to the conditions.
Mean while at the folks place in Te Anau pic.twitter.com/rNV56vYoYo— Shayden Whipps (@ShaydenWhipps) April 12, 2015
The snow is starting to fall up here on Mt Ruapehu! With more forecasted for tonight! pic.twitter.com/6fFFrsg2bR— Mt Ruapehu (@MountRuapehu) April 12, 2015