Snow on way for South Island

Chilly weather is heralding winter's approach, with frost and snow likely for the south of New Zealand next week.

Meteorologists stopped short of describing it as an arctic blast, but said the cooler air coming from the South Pole would be widely felt, with temperatures plunging by 5 to 10 degrees Celsius.

Niwa meteorologist Ben Noll said there would be two blasts of cold weather - one early next week with another more aggressive one at the end of the week.

"Certainly colder conditions than it's been, especially in the South Island where there may be some frost and some snow in the higher elevations. In the North Island, no snow just yet, but you are certainly going to want to bundle up."

He said it might be time to flip the summer wardrobe of T-shirts and jandals and pull out the winter gear.

Mr Noll said the temperatures, which could dip below zero in the central plateaus and areas in the south prone to chillier weather, would be felt more acutely due to recent milder weather.

The warmer weather was one positive from the recent flurry of storms, he said.

"It's a flow-on effect from the storms that we've had. They brought a lot of rain, but they come from the north and brought with them more tropical warmer air."

However, the fine weather was set to give way to heavy cloud and rain by the end of this week, making for a short-lived reprieve barely a fortnight on from the devastating Cyclone Cook.

MetService meteorologist April Clarke said it would turn wet on Thursday or Friday, particularly at the southwestern end of the country.

"On Wednesday and Thursday, most of the country remains sunny apart from areas of morning cloud or fog," she said. "However, places west of the Alps deteriorate into rain with a front approaching from the west."

Parts of New Zealand worst hit by the torrential rain in recent weeks won't escape either, as the MetService predicts heavy rain in the northeast later in the week.

"There is then a moderate risk that rainfall accumulations will reach warning amounts in the north of Westland, Buller, Nelson, the north of Marlborough and over the North Island from Taranaki across to the Bay of Plenty northwards."

Milder weather would return in mid-May and it would be relatively dry.

In the main centres today, Auckland was expected to be relatively warm and sunny with a high of 21degC;  in Wellington a few more clouds were forecast and a high of 17degC;  Christchurch would start the day with low cloud and fog, but this would give way to the sun later on and a high of  17degC;  while Dunedin would be sunny with a high of 19degC.