It's been an icy start to the day for many, with unusually cold spring temperatures in parts of New Zealand well into the negatives.

Clear skies and light winds made for some particularly freezing conditions in the heart of the South Island, with Christchurch the most frigid of the main centres on -4.6C at 6am.

In the more remote spots, Nelson Lakes reached -7C, Mt Cook Village got down to -5C and Culverden -4.9C.

Meanwhile, the North Island was a touch warmer, with the coolest spot being Taupō at -3.5C, followed by the Desert Rd at -2.6C.

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Auckland was significantly warmer, but still at 4C - more than half the average September low.

The good news though is that pretty much everywhere should turn into a stunning Saturday, meaning those who decided to hit the ski slopes are in for a treat.

"Most places are in for a really nice day, especially in the North Island," MetService meteorologist Tam Peltzer said.

In Auckland, there would just be a few cloudy periods and showers in the morning before clearing for a fine day and high of 13C.

Similar conditions were forecast for most, with just some cloud in western areas moving in by the evening.

In the South Island, most spots were in for a fine day, once it warms up, with just a bit of cloud and isolated showers in the west late afternoon.

Much of the same was forecast for Sunday, except for the lower South Island where a front, preceded by strong northwesterlies, is due to arrive in the morning, bringing bursts of heavy rain to the west, lasting to early Wednesday and falling as snow about the Alps.

Wednesday was looking particularly poor, with strong westerlies tending southwesterly, and snow showers affecting higher roads.

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Rainfall could reach warning levels about Fiordland, south Westland and the Otago Headwaters over Sunday and Monday, and potentially Tuesday.

Further north, there was a moderate risk of warning levels of rain about the remainder of Westland, Canterbury Headwaters and Buller during Monday and Tuesday.

There was also potential for gale-force winds about exposed parts of Southland, the Fiordland lakes, Otago and the south Canterbury Plains during Monday, and slightly higher risk about the remainder of Canterbury, Marlborough, Wellington and Wairarapa (including the Tararua District) during Monday and Tuesday.

Auckland could see some showers from Tuesday, bringing a little more relief to the water crisis with the city's dams still 22 per cent below average for this time of year.

Residents have continued to smash the requested savings however, with average water use over the past week at 382 million litres a day (MLD), well below the target of 405MLD.