Forecasters say Mother Nature is "shifting into a new gear", with the temperatures set to plunge and weather warnings possible.

Heavy rain, wind and snow are on their way for parts of the country as an autumn storm moves in.

On social media. the National Institute of Water and Atmospheric Research says Mother Nature will be "shifting into a new gear" this weekend now that summer is over.

A band of heavy rain will move over the country on Saturday and Sunday, while wind, colder temperatures and snow to high elevations can be expected at the start of next week.

MetService's severe weather outlook says the South Island will be affected by rain and wind on Saturday, with the heaviest rain expected in the northwest.

The front will then move onto the North Island on Sunday, bringing rain and possibly severe northwest gales.

It's possible that rain warnings might be issued for the area from southern Waikato to Kāpiti.

On Monday, an "intense" front, accompanied by heavy rain and northwesterly gales, would move northeast over the country, says the MetService.

"In addition, there is moderate confidence that northwest gales will become severe in Fiordland and for the east of the South Island including the Southern Alps from Marlborough to Southland.

"There is also a moderate confidence that northwest gales will become severe for Wellington, Hawke's Bay south of Hastings and Wairarapa including the Tararua District."

Moderate confidence meant there was a 40 per cent likelihood of a weather warning being issued.

Temperatures are also expected to plunge next week as the front moved through, with some places barely into the double digits.

However, the forecast for Friday - the first day of the meteorological autumn - was looking settled ahead of the storm.

Much of the country would experience either a fine or partly cloudy day.

Alexandra will be among the warmest places in Aotearoa, with a high of 28 degrees Celsius, while Tauranga and Blenheim will have a high of 27.

-RNZ.