Heavy rain, strong winds forecast for parts of South Island

South Islanders are in for a wet and blustery day, with heavy rain and strong-wind warnings in place for much of Te Waipounamu.

Torrential rain could cause surface flooding and slips, while severe gales are expected to whip up the island at speeds of up to 130km/h in exposed places.

The MetService has issued a heavy rain warning for the headwaters of the Canterbury lakes and rivers, Westland, the Buller ranges, Fiordland and the headwaters of the Otago lakes and rivers.

Strong wind warnings are in place for Marlborough, the Canterbury High Country, the Canterbury Plains and Christchurch, Otago, Fiordland and Southland.

Meanwhile, in the lower North Island including Wellington, Wairarapa and the Tararua District northwest gales are forecast to be severe with gusts reaching up to 120km/h in exposed places.

The MetService said this could damage trees, powerlines and unsecured structures.

The MetService tweeted that the strongest wind gust recorded up until 2.30pm today was 133km/h at Mount Cook Aerodrome.

Niwa meteorologist Chris Brandolino said there was an elevated risk of sharp rises in rivers and localised slips but it would not be widespread.

"There will be a good drop of rain that occurs along the west of the South Island over the next 24 hours."

He told Morning Report that rain would come with windy conditions.

"Along the east of the South Island and lower North Island ... there will be some increased fire risks, so you're going to have to be mindful of that."

He said people planning to tramp in those areas should check the forecast for heavy rainfall and high winds.

"But it's a fast-moving system so it won't be around terribly long."

In Wellington, however, Brandolino said the winds would be "quite eventful over the hours later today, I suppose into early tomorrow - you could see some wind gusts, triple digits. Winds at that speed haven't been too common recently".