The large fire that has charred around 200 hectares on the outskirts of Wanaka could still take days to extinguish.

Eight helicopters continue to battle the blaze on Mt Roy, while five crews are tackling the fire on the ground.

Fire and Emergency spokesperson Michele Poole said they will be fighting the blaze until tomorrow at the earliest.

"Although those people are no longer seeing active flames, this is a deep-seated fire and the assessment is it's going to take an awful lot of rain."

Conditions in the area are making it tough for the fire to be quenched completely, with warm temperatures making it tough work for the crews involved.

"It just feels incredibly hot. The wind is getting up and it's a hot wind. It'd be a lovely day if you are sitting by the lake but it's not much fun if you are fighting a fire," Poole said.

The fire is forcing boaties out of the water.

Harbourmaster Marty Black said his staff are at nearby Roys Bay telling boaties to keep clear to allow helicopters to fill their monsoon buckets.

"There's quite a number of them working there, obviously its a hazard they don't need with boats and that around while they are trying to load monsoon buckets."

There may be some respite for the firefighters. MetService has issued a thunderstorm watch for the area.