Metservice is warning people from the top to the bottom of the country to prepare for cold temperatures today and tomorrow.
Meteorologist John Law said severe weather warnings were in place for snowfall in Southland and Clutha and that was expected to move up to Dunedin this evening.
And this afternoon heavy rain was hitting the central North Island.
"You will find as you go through the night that will turn to snowfall around the higher central parts," Mr Law said.
Snow was expected later on the Desert Rd and on the central North Island's eastern ranges.
Cold temperatures would also creep up north as today wore on and even Northland and Auckland won't be spared from the falling mercury.
"You are going to find it's a couple of not only cold nights, but cold days as well."
Mr Law said in the Wellington region, caution should be taken when driving over the Rimutaka Hill Rd.
Tomorrow the snow in the South Island could reach low levels around Canterbury and sleet was forecast for Christchurch.
Philip Duncan, from Weatherwatch, said snow flurries were forecast for the North Island until a slightly warmer air mass arrived on Thursday.
"We're only talking a degree or two's difference but that's enough to change snow levels," he said.
"We are the only forecaster not predicting this as a serious event. This is going to be fun rather than serious."
Mr Duncan said a lot of farmers would miss out on snow completely.
"The only serious thing is for motorists - watch out for ice."
In the Wellington Region, snow was likely around the ranges down to about 300 metres from tomorrow night afternoon and into tomorrow night, Mr Duncan said.
After that snow showers could reach even lower levels on Thursday in areas further inland, such as the Hutt Valley.
"In saying that, downtown Wellington, those with high-rise buildings, there's no reason why they wouldn't be part of that as well."
And if scrawly showers were to get caught in a down draft, dustings of snow could go as low as sea level.
