The term ‘climate’ refers to long-term weather patterns, including:
In contrast, the term ‘weather’ means the specific atmospheric events at a particular time. As Mark Twain wrote in 1887, ‘Climate lasts all the time and weather only a few days’ 1
As a small land mass surrounded by oceans, New Zealand enjoys a temperate maritime climate. Mean annual temperatures range from 10°C in the south to 16°C in the north. The coldest month is usually July, and the warmest is January or February.
Sunshine hours are relatively high in areas that are sheltered from the rain-bearing westerlies. Most of New Zealand has at least 1,800 hours annually.
New Zealand’s National Institute of Water and Atmospheric Research collects climate data: over 270 million records from 5,900 land-based stations, and over 10 million records from ships. The Meteorological Service forecasts the weather.
Most areas have between 600 and 1,600 millimetres of rainfall, spread throughout the year, with a dry period during the summer. Over the northern and central areas of New Zealand, there is more rain in winter than in summer. But for much of the southern region, winter is the driest season.
Snow falls mostly in the mountain areas. It rarely falls on the North Island coasts, or western parts of the South Island. The east and south of the South Island often have some snow in winter. Frosts can occur anywhere (although rarely in Northland and Auckland), and usually form on cold nights with clear skies and little wind.
The three key factors determining New Zealand’s climate are the prevailing winds, the surrounding oceans, and the country’s mountain ranges.
The wind and oceans are affected by a global system of circulation. Heat or excess energy from the sun reaches the tropics every day and is then carried by wind and ocean currents to the cold, energy-deficient polar regions.
Lying in the middle latitudes of the Southern Hemisphere, New Zealand is buffeted by strong winds coming from the west, known as the roaring forties and furious fifties. These dominate the circulation of atmosphere.
Travelling low-pressure systems, known as cyclones or depressions, develop in these winds as they head towards New Zealand. When they pass across or south of the country they bring rain and stormy weather. On reaching the barrier of the mountain chains they rise, dropping rain on the west coasts – especially in the South Island.
Just north of New Zealand, near latitude 30° south, there is a belt of high pressure and lighter winds, where anticyclones bring fine weather. Occasionally, a tropical cyclone approaches from the South-west Pacific, resulting in severe wind gusts and heavy rain.
In line with measurements worldwide, New Zealand temperatures rose substantially during the 20th century, increasing by about 0.7°C between 1920 and 2000. The warmest year (up to 2003) was 1998, closely followed by 1999. Climate change has produced other effects: fewer frosts, retreating glaciers and snowlines in the South Island, reduced alpine snow mass, and a rise in sea level of 14–17 centimetres.
New Zealand has distinct climate regions.
This variation is caused by:
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.
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.
New Zealand’s climate varies with fluctuations in the prevailing westerlies, and in the strength of the subtropical high-pressure belt. Many of these are short-lived or random. Others are linked to general variations over the southern hemisphere or Pacific Ocean. These are persistent and predictable to some degree.
The Antarctic Oscillation (also known as the High Latitude Mode) is the alternate weakening (negative phase) and strengthening (positive phase) of the westerlies, roughly every month. Over the last 30 years there has been a trend towards a stronger positive phase – stronger westerly winds at latitude 50° south. This has been attributed to increased greenhouse gases and ozone depletion in the stratosphere.
The most important climate patterns in New Zealand come from the central Pacific Ocean.
The Southern Oscillation, or the El Niño–Southern Oscillation, is a tropical, two-phase pattern that affects air pressure, winds, sea temperature and rainfall. It follows an irregular 3–7-year cycle.
In the El Niño phase, the easterly trade winds weaken. Sea temperatures in the eastern tropical Pacific become several degrees warmer than normal. There is a systematic eastward shift of heat and moisture out into the Pacific. Australia experiences higher air pressure and drought, whereas New Zealand experiences stronger than normal south-westerly winds. This generally results in lower temperatures for New Zealand, and drier conditions in the north-east of the country.
The La Niña phase is essentially the opposite of El Niño. New Zealand experiences more north-easterly flows, higher temperatures, and wetter conditions in the north and east of the North Island. Air pressure tends to be higher than normal over the South Island, which can lead to drought conditions in the south, and also in the Wanganui–Manawatū district. Therefore there can be droughts in both El Niño and La Niña phases.
Unusually warm or cold sea temperatures influence weather systems passing over a region. This can affect the climate far away. For example, warmer conditions in the subtropical Indian Ocean in autumn often result in high-pressure systems north of New Zealand in winter. There is a stronger north-westerly airflow and increased rainfall on the West Coast of the South Island.
Between 1978 and 1998, El Niño events increased. There has been much debate about whether this was a result of global warming.
Another possible explanation is the natural variations in the climate over decades (10-year periods). The Interdecadal Pacific Oscillation is a 15–30-year cycle that affects parts of the Pacific Basin.
Three phases have been identified during the 20th century – a positive phase (1922–44), a negative phase (1946–77), and a positive phase (1978–98):
Major fluctuations in New Zealand’s temperature and rainfall appear to coincide with these phases. Increased temperatures around 1950 occurred soon after the second change, from a positive to a negative phase. Distinct rainfall changes (wetter in the south-west, drier in the north-east) coincided with the switch from negative to positive in the late 1970s.
Three important areas of activity are affected by New Zealand’s climate: recreation, health and the economy.
What we choose to do for fun often involves getting outside, and the particular outdoor activity we choose is strongly influenced by the local climate. For example, the style of rugby played in Southland with its rain and muddy grounds is different from that in the much drier Canterbury. Aucklanders love to sail because of the regular winds and warm air and sea temperatures in the Hauraki Gulf, and trampers in the South Island’s West Coast can explore some of the lushest rainforests in the world because of regular rainfall there.
Gardening is a hugely popular recreation, and garden styles are influenced by the varied regional climates. The South Island, with well-defined seasons, brings the reward of spring flowers and brilliant autumn foliage. Auckland’s high rainfall and warmer temperatures allow gardeners to enjoy year-round greenery and cultivate subtropical plants such as bougainvillea and hibiscus.
How chilly do New Zealanders get before they switch a heater on? A study suggests that it depends on what they’re used to in different regions. Aucklanders in the subtropical north may feel cold at a higher temperature than frost-hardy Dunedinites down south. But wherever they are, Kiwis turn on the heat at about the same time in the autumn – when temperatures drop significantly below their local average.
A disadvantage of living in New Zealand’s mild climate is that when served up extreme weather, such as a bitterly cold southerly spell or an intense heat wave, people can find it hard to cope. The oldest and youngest citizens in particular can suffer from ill health as a result.
When the average air temperature drops below 10°C, hospital admissions in the Auckland region rise dramatically, mostly for respiratory ailments. One cause is insufficient insulation in homes designed for a mild climate, and not for the infrequent extreme conditions.
Some significant activities influenced by climate are:
Acknowledgments to Jim Salinger, Stuart Burgess, Jim Renwick and Michael Uddstrom
Brenstrum, Erick. The New Zealand weather book. Nelson: Craig Potton, 1998.
Gentilli, J., ed. Climates of Australia and New Zealand. Amsterdam: Elsevier, 1970.
Karoly, D. J., and Vincent, D. G., eds. Meteorology of the southern hemisphere. Meteorological Monographs no. 49. Boston: American Meteorological Society, 1998.
Sturman, A.P., and N. J. Tapper. The weather and climate of Australia and New Zealand. Melbourne: Oxford University Press, 2006.