MetService advises that a band of very active thunderstorms is moving slowly northeast over Whanganui, Taranaki, Taihape, Taumarunui and Waitomo this afternoon, with heavy rain, hail, squally wind gusts and frequent lightning.

"Although the rain, hail and wind associated with the thunderstorms may not reach severe thunderstorm criteria, the thunderstorms are producing widespread frequent lightning which could cause localised damage and affect power and internet connections," says a MetService spokesperson.

MetService advises that should severe weather approach, or if you feel threatened, take shelter immediately. 

The thunderstorm activity will ease from the south during the afternoon as the line of thunderstorms moves north. 

MetService says a front is expected to bring rain to Fiordland and the Westland District on Monday.

"There is low confidence of rainfall accumulations reaching warning amounts there," says a MetService spokesperson.

"There is moderate confidence that westerly gales will become severe for a time in the morning about the south coast of the South Island. There is low confidence that severe northwesterly gales will affect the Canterbury high country, Wellington and Wairarapa."

On Wednesday a ridge of high pressure will be bringing settled weather to much of the country.

An active front is expected to move northeast over the South Island on Thursday, followed by cold southwesterlies that may bring showers and snow to low levels for Otago and Southland.

"While warning amounts of snow are unlikely the bitterly cold winds and snow may bring stress to livestock. Roads may also be affected," says a MetService spokesperson.

"There is moderate confidence that warning amounts of rain will accumulate in Buller, Westland, Fiordland and about the headwaters of the Canterbury and Otago lakes and rivers.

"There is low confidence in warning amounts of rain affecting Southland. There is moderate confidence that severe northwesterly gales will affect the Marlborough Sounds, Wellington and Wairarapa south of the Tararua District."

On Friday September 27, a front is expected to move northeast over the North Island and bring rain to many areas while cold showery southwesterlies affect the South Island. Severe weather is unlikely.