Milford Sound weather is always a hot topic as it is amongst the wettest locations in New Zealand and around the world. So should that put you off adding it to your destination list? Absolutely not. In fact we cannot stress enough how important it is to make sure you still visit on a wet day!
Milford Sound Total Rainfall
Milford Sound's mean rainfall is 6720mm (22 feet or 6.72 metres), with 182 days on average recording at least 1mm of rain. It is also very unpredictable, with offshore westerly breezes quickly pushing weather systems off the West Coast of New Zealand into Milford Sound and trapping it inside the basin surrounded by 2000 metre high mountains.
It would be understandable to think that staying away from Milford on a day like this would be warranted however that couldn't be further from the truth. Milford Sound comes roaring to life in the wet, literally, with hundreds more waterfalls being fuelled by the mountain top lakes.
Waterfalls line the Fiord corridor right out to sea and can only be witnessed via one of the many cruise offerings available.
Milford Sound weather no matter what is always very dynamic, in the morning you can have pouring rain, and by afternoon the sunshine is ripping down the Fjord.
As well as cruising, kayaking is another popular way to witness the waterfalls although this is best done with one of the tour operators in Milford due to their experience and knowledge of safety around one or two of the particularly big, powerful waterfalls that have a tendency to pull you in quickly towards the impact area of the fall.
Why does it rain so much in Milford Sound?
Milford Sound sits between a large mountain range and the Tasman Sea. While winds travel across the sea, particularly from Australia, they collect large amounts of moisture before hitting the West Coast of the South Island, but in particular the Southern Alps. The cooler mountain ranges force the warm, moist air up and turning it cold also, causing the change to rain.
The systems then often get caught in the basin area of Milford Sound, the Hollyford Valley and the Eglinton Valley, resulting in large dumps of rain. Due to the mountain traps, they struggle to escape until they effectively run out of rain.
Compare Milford Sound to its nearest township of Te Anau and it is starkly different with the latter only receiving about 1200mm of rain per year, about the average for New Zealand which surprises a lot of people, the assumption being that Te Anau is right up against the National Park and so therefore must rain a lot. The reality is that the mountains that flank Te Anau to the west, tend to again trap the weather systems that come in instead.
Freshwater / Saltwater Dynamic
With the amount of rain in Milford Sound, freshwater is abundant and while the fiord is connected to the Tasman Sea, the saltwater gets trapped down and takes about 10 metres of diving before hitting it. The other dynamic at play is, due to the vast majority of freshwater coming from mountain run off, the water that has settled above the salt level is stained dark from leeching of the mountains. This means that wild and fish life that ordinarily would have spent most of their day well below the surface, come up towards the waterline because the staining causes the deeper levels to be much darker and colder than normal.
It is quite common to find penguins, seals and even dolphins playing or lapping around parts of the fiord, following a large rainfall period.
While you will certainly need a jacket, good footwear and an open mind when visiting Milford Sound in the wet, be prepared to have a magical day in amongst the waterfalls and misty clouds. Our article 'What are the best stops on a wet day to Milford' is worth a read to plan out your day.