Today the ridge of high pressure over the North Island will start to weaken, and a northwest flow will affect central and southern New Zealand, according to MetService meteorologists.

"A front is expected to bring rain to Fiordland, and there is low confidence of warning amounts of rain there."

The Bay of Plenty begins with a fine morning, with cloud increasing from the afternoon.

On Wednesday, a large low pressure system is set to move onto central and southern New Zealand, while an associated front moves onto the North Island.

Tauranga is forecast to have rain developing in the morning, with heavy falls expected overnight.

"There is low confidence for warning amounts of rain in Northland, western Bay of Plenty, the central North Island hill country, the Tararua Range, Tasman/Nelson, also for Buller and the ranges of from Grey to central Westland.

"Confidence is moderate to high however of rainfall reaching warning amounts in Fiordland, Taranaki Maunga, the west of Tasman and northwestern ranges of Marlborough, also for eastern Bay of Plenty."

MetService said in addition, a period of snow is likely for the Canterbury High Country late in the day, and there is low confidence of warning amounts of snow above about 800 metres in the South Canterbury High Country.

"There is low confidence of severe northwest gales in Northland, and severe northerly gales in Taranaki, inland Whanganui, Taihape, the Marlborough Sounds, Wellington and southern Wairarapa."

On Thursday, June 5, MetService said the low pressure system and associated front should move away to the east of New Zealand in the morning.

"There is moderate confidence of warning amounts of rain in eastern Bay of Plenty at first, and low confidence for the Tararua Range.

"In addition, a period of snow is possible for the Canterbury High Country early in the day, and there is low confidence of warning amounts of snow above about 800 metres in the South Canterbury High Country.

"A cold showery west to southwest flow then spreads across the country."

On Friday, a very cold and showery southerly flow is forecast to spread over the South Island.

"Snow is possible for the hills and ranges from Southland to Canterbury and eastern Marlborough, and possibly to near sea level in Canterbury. Snow however, is not expected to approach warning criteria. Showery west to southwesterlies affect the North Island."

There is minimal risk of severe weather on Friday.

On Saturday, the cold southerly flow should spread northwards across central and northern New Zealand, with showers for southern and eastern parts of both islands, along with snow possible for high level roads.

MetService said there is minimal risk of severe weather on Saturday.