Weather: Wind and rain to lash New Zealand as 'complicated' low moves in

Wind and rain are set to lash much of New Zealand as a low in the Tasman Sea brings a change to Aotearoa's weather.

A front affects the South Island on Wednesday and Thursday and is expected to bring heavy rain to western and southern areas. Cold southeasterlies are also forecast to bring snow to 300 metres in Southland and Otago from Wednesday, and there'll possibly be heavy snow above 600 metres for inland Canterbury and Otago on Thursday.

It means there'll be a good dusting of snow for the ski fields - and even a little bit for those up in the North Island too, WeatherWatch head weather analyst Philip Duncan said. Ski fields in the South Island could expect between 20cm and 50cm of snow.

But before the southerly arrives, Duncan said temperatures will remain above average for New Zealand. Currently, temperatures for much of the South Island and some eastern parts of the North Island are 4C to 8C warmer than usual for this time of year.

By Thursday, the front will turn into a low pressure zone and a windy northerly arrives at the top of the North Island.

"This low is a little complicated. It's not your traditional cold front that just moves straight up the country," Duncan said.

And by Friday, the low to the North gets larger and there's a windy easterly blowing through. This means there'll be patchy rain and showers in those areas on Friday, Duncan said, and the windy easterly will still be around on Saturday.

The low will move even further to the east by Sunday.

MetService warns that all regions exposed to the east will see rain before the week is out, and Northland and Auckland in particular could get heavy rain on Thursday and Friday as the rain band moves up north.