They measure rain in metres, not centimetres, on the South Island's West Coast. It might be a mere two metres close to the sea but a whopping 18 metres inland.

West Coasters (and I can claim to be at least 25 per cent of one) get rather tired of visitors complaining about the rain. After all without the rain there'd be no luxuriant rainforest and it's the rain transforming into snow at high altitudes that has helped create the Franz Josef and Fox glaciers.

My mother always claims that as most West Coast rain falls at night, this deluge of rain is not nearly as disruptive to travellers as it might appear (unless of course one is intrepidly, and potentially rather damply camping). Growing up in Greymouth she used a simple form of weather forecasting - if you couldn't see the Seven Sisters Range behind town it was raining and if you could, it was probably about to rain.

So, when we arrived in South Westland last week in the midst of a downpour it was no surprise. The Alps were invisible, the forested foothills wreathed in low cloud and the windscreen wipers were having trouble keeping up.

But whereas on the Canterbury side of the mountains a southerly can and often does linger gloomily and chillingly for days, the weather on the Coast can change dramatically.

The morning after the deluge I opened the curtains on a sparkling morning, the mountains were almost blindingly white with a fresh coating of snow and Franz Josef looked freshly washed. Not far away a helicopter thrummed into the sky and there was a drone of a small plane somewhere overhead. The scenic flights were up and running, making the most of the perfect conditions. Which don't occur that often, despite my mother's claims.

On a day like this, I pondered, Aoraki Mt Cook would be completely clear. But scenic flights were for tourists, expensive too and probably fully booked for the day...

And so, an hour later we were preparing to board a four-passenger Hughes helicopter along with pilot Ben.

Remarkably, the other passengers were also Kiwis - a couple from Nelson celebrating their 60th wedding anniversary. Both in their 80s, it was their first time in a chopper.

Our flight took us low across the podocarp-clad hills between Franz and Fox Glaciers, the Tasman Sea gleaming to our west. We then turned towards the mountains, flying up the length of the Fox Glacier, its surface grey with trails of moraine. Ahead loomed the bulk of Aoraki Mt Cook. It's not until you fly around our highest mountain (or are among the intrepid few who climb it) that you realise just how it dominates the Southern Alps.

Beyond the Hooker Glacier and valley we could see Lake Pukaki and as the chopper began to turn north the Tasman Glacier, New Zealand's longest came into view. Icebergs bobbed in the lake that has formed below its terminal face.

Ben pointed out the route taken by most climbers heading for Aoraki's summit, indicating shape of an alpine hut perched on a ridge to give us some perspective. My respect for climbers redoubled. We flew between Aoraki and Mt Tasman, New Zealand's second highest peak and were at the head of the snowfield that feeds the Franz Josef glacier.

Pristine snow, sculpted gently by the wind, lay between the encircling walls of the Alps. Where the underlying ice had begun to move downhill under its own weight there were deep chasms where it seemed to be ripping away from the rock.

Where the glacier begins a steep drop into the valley the ice was riven into crevasses, their depths a translucent aquamarine. Just below the peak of Mt on the southern side of the Franz Ben landed the helicopter. In front of us the snowy slope fell away and beyond lay Aoraki and Tasman again, sharply etched against the sky. We sunk up to our knees in the snow taking photographs while the chopper's rotors spun on what I guessed was the equivalent to a car idling at the lights. The diamond wedding couple never stopped smiling the whole time.

We took off, flying down a hanging valley and shooting into the void above the glacier. Below us was the spot where I'd eaten lunch just a day earlier. It had taken hours for me to reach it; it took the helicopter mere seconds before we were over the terminal face of the Franz that I'd puffed my way up.

As we swung in over the Waiho River beside the Franz township Ben pointed to the oxidation ponds on our left and commented that he'd seen a kayaker paddling across them a few days earlier. After we landed I looked back to see Ben being kissed soundly on the cheek by the diminutive Nelson octogenarian on tiptoes - wedding anniversary or not she'd clearly been smitten.

Pictured above: Cloud scuffs over the snowfield at the head of the Franz Josef glacier.
Jill Worrall

Click here for photos.