The lower west of the South Island can expect a heavy deluge of rain over the next 24 hours, with up to 330mm in some regions.

A front moving towards the lower half of the island will bring thunder and heavy rain according to MetService.

Meteorologist Andrew James said Westland and Fiordland are in the front’s firing line and heavy rain warnings have been issued for both districts.

Fiordland won’t get as much rain, according to James, but 70mm and 100mm will fall from 10pm until early tomorrow.

Meteorologist, Andrew James said Westland and Fiordland are in the front’s firing line. Photo / Niwa

Those Westland have more to worry about - rain will reach levels of up to 350mm around the glaciers.

Westland’s rain will kick off around midnight tonight, according to MetService projections and is set to continue until Thursday afternoon.

James believes the downpours should ease around tomorrow evening for the most part in Westland.

“The rainfall amounts aren’t out of the ordinary for Westland,” the meteorologist said.

 “A couple of areas are also under watch - Buller, Nelson Lakes and also at risk are the Canterbury lakes and the Southern Alps.”

An impressive graphic published by Government weather forecaster Niwa shows regions around Milford Sound will get 100mm of rainfall by 1am Thursday.

Niwa’s social media post describes the rainfall amounts about the ranges as “impressive”. Photo / Niwa

The lower-central western regions of the South Island, including Fox Glacier and Mt Cook, can expect the most extreme rainfall.

Niwa’s social media post describes the rainfall amounts about the ranges as “impressive”.

“Localised slips and flooding are possible,” the weather forecaster said.

The rainfall is on-trend with the nation’s wet and windy start to 2023, with flooding and cyclones hammering the North Island over recent months, causing widespread devastation.

Cyclone Gabrielle was expected to reach the South Island at the conclusion of its journey but its effects were barely felt across the districts.