Residents living in Waihopai Valley in Marlborough, where a forest fire is raging, have been warned: if there is a change in weather they might have to evacuate their homes.
The fire, which started at 11.30 yesterday morning, is estimated to have travelled through 1200ha of pine forest and farm grassland, moving from the Wairau Valley towards the adjacent Waihopai Valley.
It's the biggest fire Marlborough has faced since the Boxing Days blazes of 2000.
Marlborough principal rural fire officer Richard McNamara said that while there was no immediate threat to properties, a plan had been put in place to evacuate residents if a change in weather pushed the flames in the direction of the homes.
"This fire is burning far more intensely and it has a hundred times the fuel loading in front of it compared with the light grassland on the Wither Hills but fortunately it's well away from any settlement," he said.
Up to a dozen farm houses and lifestyle blocks could be in the line of the flames if the predicted strong nor'westerly winds were to take the fire into the Waihopai Valley tomorrow," he said.
"The forecast is for perhaps 20ml of rain tomorrow night but I suspect we might be lucky to get 3ml and what we really need is 300ml -- it's extremely dry up there and if that wind gets up, it will put pressure on the fire lines."
The fire management team had identified trigger lines lower down the Waihopai Valley at which point police would make an evacuation order.
"We're not expecting that to be necessary before late tomorrow, if at all," Mr McNamara said, "but we are preparing for all possibilities as this is a very big fire and the safety of human life is paramount."
In the event of an evacuation, brigades from Blenheim and Renwick would be called in to protect houses, he said.
Ground crews were still unable to be deployed due to safety considerations. However, up to 100 crew, 15 aircraft and heavy machinery were on hand to fight the blaze.