Five helicopters and seven fire crews are fighting a 30-hectare pine forest fire east of Martinborough.
Two further helicopters are expected to join firefighters shortly.
Wairarapa principal rural fire officer Phill Wishnowsky said it could take days to extinguish the large forestry blaze.
"We've got a large forest fire, very active and quite extreme conditions.
The fire is an active fire so of course everywhere it goes it's obviously destroying the forest.