Southland is under a heavy rain watch as the second of two weather systems bears down on the country.
Forecasters say the amount of rain may approach warning criteria, from 4pm tomorrow though to 3am Saturday.
Elsewhere parts of the South Island are being warned to expect "huge" amounts of rain and gale-force winds.
A front moved northwards over the South Island yesterday and was set to continue today, while the second system is expected tomorrow, bringing further heavy rain, strong winds and large wave conditions.
MetService said heavy rain was expected for most of the West Coast starting this morning and continuing through until Friday or Saturday.
There was a risk of surface flooding and slips on much of the West Coast, MetService meteorologist Alanna Burrows said.
She said people should avoid low-lying areas and drive cautiously on the roads.
The areas likely to experience the heaviest rain on Thursday would be Westland and the Tasman District, Burrows said.
The Tasman District could see up to 400mm, which was a "huge" amount of rain, while Westland was looking at between 500mm and 600mm for the combined events.
Orange heavy rain warnings, updated late on Thursday morning, were in place for Tasman District northwest of Motueka, Buller District, the Nelson and Marlborough Ranges, Grey District, Westland District, and the headwaters of the Canterbury lakes and rivers.
There are orange strong wind warnings for many areas of the upper South Island and the Wellington region of the North Island. Severe gale north to northwesterlies could gust up to 140kmh in exposed places, MetService said.
Burrows said things would ease off on Sunday.
NZ Transport Agency Waka Kotahi said it encouraged motorists to prepare for adverse conditions on roads.
The agency said heavy rain meant slippery roads, and drivers should think about adjusting speeds and travelling distances, avoiding sudden braking, and staying visible.
It also urged road users not to try to travel through floodwaters where the risks may not be obvious.
- additional reporting Allied Media
