A group of whales has been stranded around Farewell Spit, near the top of the South Island, for the third time in two months.
About 90 pilot whales were seen milling close to the shore around noon on Monday and have since grounded on a receding tide, Project Jonah chief executive Kimberly Muncaster says.
Ms Muncaster says volunteers will care for the whales until nightfall, when the fast incoming tide will be a danger to the people.
"There's a small chance the whales may refloat on tonight's high tide at 11pm, but we will be back at first light to assess the situation and assist DOC (the Department of Conservation) in their rescue response," she said on Monday.
"Hopefully we'll be able to keep as many whales as possible alive until nightfall."
Project Jonah marine mammal medics have also been called to give the whales first aid.
Volunteers with wetsuits are wanted, as are those who can work at the beach.
They're asked to check out Project Jonah's website for a list of items they will need, which includes food, water, sunscreen and appropriate clothing.
The spot where the whales were stranded is close to Farewell Spit, where 25 were stranded early in January. Seven of those whales died, while 65 whales died after becoming stranded in the same area in November.
Farewell Spit is known as a whale stranding hotspot.