MetService has issued a severe weather watch for parts of New Zealand.

Significant heavy rain and severe gale northwesterlies are expected for parts of southern and central New Zealand.

"An active front is forecast to approach the South Island from the south Tasman Sea on Sunday, then move northeast over the Island from late Monday to Tuesday," says a MetService spokesperson.

"This front, preceded by a strong, moist and unstable northwest flow, is expected to bring significant heavy rain to western and central parts of the South Island and severe gales to Fiordland and eastern areas of the South Island, also Wellington and southern Wairarapa."

Warnings for heavy rain and severe gales are in force for many parts of the South Island. Strong wind watches are now in force for Marlborough, Wellington and southern Wairarapa.

"This is likely to be a significant severe weather event," says a MetService spokesperson. "People are advised to keep up to date with the latest forecasts, as some areas could be upgraded to Red Warning, and more areas added."

A strong wind watch has been issued for these areas:

Marlborough
Valid: 32 hours from 2:00 am Monday to 10:00 am Tuesday
Forecast: Northwest winds may approach severe gale in exposed places.

Wellington and Wairarapa south of Greytown
Valid: 27 hours from 8:00 am Monday to 11:00 am Tuesday
Forecast: Northwest winds may approach severe gale in exposed places.