Ash and dust from the Australian bushfires has increased the risk conditions for avalanches along the Milford Road. 

Milford Road authorities will be working to control for avalanches along the road that have been made worse by a new layer of ash and dust from across the Tasman.

Milford Road Alliance manager Kevin Thompson said the drifting ash and dust from the fires created an unstable and slippery layer inside the snow. 

"When we get enough snow, or rain, or sunlight on those snow layers, then they give way."

Recent rainstorms only added the risk, making for the "perfect recipe" for avalanche conditions.

Mr Thompson said authorities hadn't expected the bushfires to impact their work along the Milford Road as greatly as it had.

They were hoping to do enough avalanche control work today, once weather conditions clear, to bring down much of the snow. 

It was uncertain at this moment when the road would re-open, but they were aiming for today or tomorrow to do so. 

"And then we'll deal with the next storm as it comes in," Mr Thompson said. 

The Milford Road is an approximately two-hour drive connecting the town of Te Anau to tourist hotspot Milford Sound. 

It's the only public road in New Zealand that's actively managed for avalanches.