New Zealand has distinct climate regions.
This variation is caused by:
- the length of the country extending from latitude 34° to 47° south
- mountain chains running from north to south, which provide a barrier for the prevailing westerly winds.
Climates vary from warm subtropical in the far north to cool temperate in the far south, with severe alpine conditions in the mountainous areas.
The rainfall is even more varied. The West Coast of the South Island is the wettest area, with over 6,000 millimetres of rain annually at Milford Sound, and over 10,000 millimetres on the divide of the Southern Alps. Just 100 kilometres or so to the east of the mountains is the driest region, with annual rainfall of around 400 millimetres or less.
The temperature range at any time of year becomes more extreme as you go inland, where there are lower minimum temperatures and higher maximum temperatures – for instance at Alexandra in Central Otago and Ohakune in the central North Island.
Temperatures also drop about 0.7°C with every 100 metres of altitude.
The language of climate
Many Māori place names show an appreciation of the distinctive climatic features of the location. These include:
Aotea (white cloud), which is the Māori name for Great Barrier Island.
Hautere (swift wind), also known as Solander Island, which is close to Puysegur Point, one of the windiest spots in the country.
Ōmarama (the place of light) in South Canterbury, which is protected by the mountains from cloud and rain.
Ōhau (the place of wind), which is in South Canterbury, where westerlies sweep down from the alps.
Onekakā (red-hot or burning sand), which is in Golden Bay, Nelson.
The moderating influence of the oceans means there are relatively small variations between summer and winter temperatures (mostly less than 10°C), although inland and to the east of the ranges the variation is greater (up to 14°C).
Seasonality in rainfall is much more marked in the North Island, where winter is noticeably the wettest time of the year. This is because the rain-bearing westerly wind belt moves north in winter. In summer, the westerlies return to the south, and the North Island is usually under the influence of subtropical high-pressure systems. This north–south migration produces the so-called equinoctial gales, a strengthening of the westerlies, which is particularly marked in the spring.
New Zealand also has many microclimates within the regions. For example, Nelson (at the top of the South Island) is unusually warm because it is protected by mountain ranges to the south and west. Wellington is very windy because it is exposed to the westerly winds that are funnelled through Cook Strait.
Regional councils and individuals often require information at this level, for instance to assess locations suitable for wind power or agricultural activities such as wine growing.