Fine weather over the Tasman Sea, but heavy and dark clouds are gathered over the Southern Alps (raising steeply immediately to the right of the picture). The Karangarua River, south of Fox Glacier. Photo NC.

The specific climatic conditions that prevail in New Zealand have a marked influence on the character of the mountains, especially on the rates of erosion and associated landforms, as well as glacier cover.

Web resources : At NZ Met Service/New Zealand climate data: Mean air temperatures Climate extremes

Influence One: frequent frosts
New Zealand's climate is strongly submitted to oceanic influences.
One of the results are even temperature regimes, with cool temperatures and only moderate variations between winter and summer.
Above an altitude of 1000 metres (3280') (except in the far north) temperatures fluctuate around freezing point throughout the year.
At about 1500 m mean winter temperature is about 0 degrees centigrade, mean summer temperature 10 degrees centigrade, and above 1000 m frost can occur anywhere, anytime of the year.
As a result temperatures frequently fall below freezing point, thus favouring the formation of needle ice that pulverises bare soils, and freeze-thaw processes that result in rock desintegration.

Influence two: high (or low) rainfall
The New Zealand islands lie across the path of the prevailing winds and westerly circulation system. Consequently most precipitation falls on the western flanks of the mountain ranges, particularly in the South Island. Total precipitation above 1000 metres ranges between 1250 to 15,000 millimetres a year (49 to 590 in.), but most high country exposed to the west and close to the main divide receives more than 4000-5000 mm (157-198 in.) annually. Torrential rain sometimes exceeding 500 mm (20 in.) per day may occur.
By contrast, the ranges located to the east, especially Central Otago, are in the 'rain-shadow' and only receive 10-20% of that amount.

Result: high erosion rates
This is particularly marked in the western Southern Alps.
There high rainfall is combined with high rates of uplift (10-15 mm per year in some areas), the two major factors that control sediment yield. In turn, sediment yield is a measure of the rate of erosion. These areas have the highest sediment yield in New Zealand (equivalent to a lowering of the ground surface by as much as 11 mm per year in some areas), among the highest known in the world and met elsewhere only in a few areas of high rainfall and tectonic activity.
The geomorphology of the western Southern Alps is a model of the conjunction of high rates of uplift combined to high erosion rates: extremely steep land, intensely dissected with narrow valleys, sharp ridges, steep rivers and gorges.

By contrast in Central Otago, where precipitation is low (200-500 mmm/year), erosion rates are also low and ancient peneplain landforms have been preserved.

Result: low altitude glaciers
The mountains of New Zealand have more glaciers than other mountains of similar altitude in temperate areas. There are about 3000 glaciers larger than 1 hectare (2.5 acres), mostly located in the Southern Alps. There numerous mountains markedly lower than 3000 metres have permanent snowfields, and in areas of very high precipitation some glaciers descend to very low altitude (e.g. 300 metres (1000') for Fox and Franz Joseph Glaciers in Westland).