Weather watches issued for much of the South Island

A number of weather watches have been issued for parts of the central and west South Island.

A heavy rain warning at orange has been issued for Westland, which can expect 60 to 90 millimetres of rain about the ranges, with less near the coast - in addition to what's fallen already.

Peark rates are expected to be 15 to 25 millimetres per hour but 20 to 25 in thunderstorms and possible downpours.

Fiordland is also under a heavy rain warning at orange, with an additional 40 to 70 millimetres expected on top of what has already fallen.

"The front is preceded by strong or gale northwest winds and is expected to bring a brief period of heavy rain to southern and western parts of the South Island, plus the Tararua Range," MetService said.

"Thunderstorms and downpours are also possible in the west of the South Island."

Tararua Range, Buller, Headwaters of the Otago and Canterbury lakes, and the rivers south of Mt Cook, Southland and Clutha are all under yellow rain watches.

"Rainfall amounts may approach warning criteria."

Wellington, Wairarapa, Marlborough and Canterbury High Country are all under strong wind watches at yellow.

"Northwest winds may approach severe gale in exposed places."