A disturbed, strong and cold southwest flow will be spreading over the entire country on Tuesday, said the latest update from the MetService.

"It will then ease later in the day as a ridge moves onto the South Island."

Snow is expected to low levels over the South Island at first on Tuesday, with low confidence of warning amounts of snow above 400 metres from Southland through to south Marlborough. 

For the North Island, there is low confidence of warning amounts of snow above 700 metres for the Taihape region and the ranges of Hawke's Bay. 

In addition, there is low confidence of southwest gales becoming severe over Northland in the afternoon and evening.

Wednesday September 18 

The ridge moves over the North Island, while northwesterlies become established over the South Island, bringing rain to the western regions.

There is minimal risk of severe weather.

Thursday September 19

On Thursday, the northwest flow strengthens over the South Island as a front moves onto southern areas, bringing rain to many western and southern regions.

There is low confidence that rainfall accumulations could meet warning criteria over Fiordland and the ranges of the Westland District.

Friday September 20

On Friday, several fronts move across New Zealand, bringing bursts of rain to western regions, and strong northwest winds at times.

There is low confidence of rainfall reaching warning accumulations about the ranges of the Westland District, Buller and the Tararua range.