Westland/Tai Poutini is a place of extremes, from the highest mountains to most ancient rain forest, and certainly extreme precipitation.
Try to allow more than a day in the region to increase your chance of clear weather. Otherwise, put your rain gear on and get out in it: walking in the rain forest, or in those massive glacial valleys with waterfalls roaring down the sheer sides, is a special experience. Annual rainfall here ranges from more than 120 inches at the coast to an incredible 16 feet on the alpine summits. Huge volumes of snow are dumped each year, feeding the 140 glaciers. The snow is compressed into ice on the névé, or head, of the glaciers (New Zealanders say "glassy-urs"), then moves steadily downhill under its own weight. The best known and most visited glaciers are Franz Josef and Fox. If, however, you're driving through on a cloudy or wet day—quite likely—you will get no idea of the size of the mountain ranges looming beside you. The main stopping places are townships near these glaciers, named simply Fox Glacier and Franz Josef, the latter slightly larger. Both towns have solid tourist infrastructures. The summer tourist rush means you should make reservations in advance for lodgings and restaurants, and in winter some places close. Check ahead.