Cyclone Pam is currently in the tropics and rated a category 4 though is likely to intensify.

The Kaikoura coast could be in for large waves, significant rain and high winds when a tropical cyclone hits the South Island next week.

Tropical Cyclone Pam was north of Efate, Vanuatu's main island, and expected to slam into it in the next 12 to 24 hours.

The cyclone is expected to then curve southeast towards New Zealand, bringing high waves and heavy swells from North Cape down through the Bay of Plenty and along the East Coast on Sunday.

MetService meteorologist Peter Little said the effects of the cyclone would not be felt in the South Island until next week, when "significant rain" and southerlies were predicted for the Kaikoura coast on Tuesday and Wednesday.

"This cyclone has the potential to bring quite severe weather to parts of New Zealand. People need to keep up-to-date with forecasts," Little said.

There might be some inland rain on the South Island, but most of the rain would be on the coast.

"It has the potential to bring very large waves to eastern coasts as well," Little said.

"People considering going out on the water in the middle of next week will need to pay particular attention to the forecasts."

Marlborough-based climate scientist Stuart Powell said the impact was tracking to the south east.

"The impact on the South Island is not going to be great because the system is just too far to the east of the South Island."

The weather prediction models he had used suggested that large amounts of rain were unlikely, but the situation was "evolving by the hour".

"It's quite a changeable, moveable system."

"At this moment I can't see anything more than a few coastal showers."