Severe weather warnings are in place for Taranaki, the Tararua Ranges and much of the South Island with gales and heavy rain set to batter these areas.
MetService predicts "intense" rain will hit Westland, north of the glaciers, this evening, with up to 150mm of rain pounding the area until Sunday.
Heavy rain will continue in Buller, Nelson and northwest Marlborough until at least Sunday morning, with up to 270mm of rain expected in some areas in the 24 hours from 9am today.
Nelson Police told Radio New Zealand that trampers should abandon any plans to go into the mountainous areas as waterways could rise quickly.
Senior Sergeant Stu Koeford says any trampers already out should think about returning immediately.
A rain warning is also in place for headwaters of the Canterbury Lakes and rivers north of the Rangitata River for Saturday and Sunday morning.
"This is a significant weather event for the South Island West Coast, Nelson, parts of Marlborough and areas near the alps," the MetService website reads.
"People planning outdoor activities during this time are advised that heavy rain is likely to make conditions hazardous.
In Taranaki and the Tararua Ranges already heavy rainfall is set to intensify overnight and strong northwesterlies are expected.
NZN