UPDATED 6.22pm: Firefighters are still battling a forest fire that has engulfed a valley in rural Marlborough, but rural fire authorities are confident the majority of the blaze will be contained by tonight.

A blaze to the the north of the Wairau River, in the Waikakaho Valley, has been burning since Wednesday.

Dry conditions and wild winds of up to 100km/h hampered firefighters and pilots' efforts to contain the 453ha fire yesterday.

About 50 to 70 firefighters along with three aircraft would be battling the blaze today.

Marlborough principal rural fire officer Richard McNamara said the blaze was expected to be 80 per cent contained by 6pm today as weather conditions improved.

"We've had increasing relative humidity which means the vegetation is more susceptible.

"Wind's gone down to 10km an hour and temperature has gone down too," he said.

He said this had "given us the break we need".

The wind would pick up to 40km/h this afternoon.

Mr McNamara said a forest fire couldn't be contained with just aircraft.

"The only way you can get a fire like this out is to get the crew on ground to kill it.

"There's no way you can get a fire out with aircraft as you can't get underneath it and break it apart," he said.

He said firefighters along with heavy machinery, heavy tankers and pumps would be on ground today.

Mr McNamara estimated about 30 per cent of the fire was contained at present.

"It's looking really good."

He credited the pilots and firefighters for their work.

"It's a dangerous job but we can do it safely if we keep to the rules of looking after each other," he said.

Meanwhile a fire at a forestry plantation in Whareama Forest between Castle Point and Riversdale has now burned through 180 hectares of pine tree on land owned by Juken New Zealand.

Around 70 firefighters are on the ground and seven helicopters plus excavators and bulldozers are being used.

Juken General Manager Dave Hilliard said wind gusts of up to a hundred kilometres an hour are making it a difficult task, but "the guys working are safely through the burnt area towards the fire's burning on the flanks and towards the front."