New Zealand's Climate:

New Zealand is in the same hemisphere as South Africa and Australia, having a temperate climate with moderate, year-round rainfall and in the North Island especially, an absence of extreme temperatures. The country enjoys a pleasant and generally stable climate. Average summer temperatures will be between 20 and 30 degrees Celsius and winter temperatures between 10 - 18 degrees.

New Zealand is long and narrow, stretching a distance of 1600 kilometres in a North to South direction and being no more than 450 kilometres wide, at its widest point. The North and South Islands have a combined area of approximately 268,000 square kilometres. The sea moderates the climate bringing mild temperatures and a reliable climate throughout the year. The country is close to the International dateline and it is claimed that Gisborne, on the East Coast of the North Island is the first city in the world to see the light of each new day.

October through to April are the warmest months and May to September are the coolest. A typical summers day in the North will range in temperature between 24 and 30 degrees centigrade (72 and 86 Fahrenheit), while a mid-winters day will rarely fall below 14 or 15 degrees centigrade (around 52 Fahrenheit).

Auckland has never known snow.

In the south it can be quite different or even in the north at higher elevations. Christchurch will occasionally have snow but is generally a very dry and sunny climate. Dunedin too is very dry with low year round rainfall but it is more likely than Christchurch to experience snow in winter.

Snow is generally not seen at sea level, though there is an abundance of snow during winter in the South Island high country and in the mountain ranges in the North Island. Both the North and South Islands have ample winter ski fields, with the South Island renowned for the majesty of its mountains and beauty of its woodlands, lakes and rivers.

Nelson, at the top of the South Island is the sunniest city in the country, however most of the country enjoys over 2000 hours of sunshine per year. The country is largely pollution free but on still winter days in Auckland and Christchurch air quality can certainly be at levels we should not be proud of.

 Table 1. Average rainfall and average sunshine hours

NIWA analyses of 2008 month-by-month records and preliminary end of year data show:

In summary, 2008 was sunny and warm, but a rollercoaster year for extremes.

Key points include:

• It was sunny or very sunny over much of the country, with near record or record sunshine totals recorded in the central North Island, parts of Hawke's Bay and the south of the South Island. The national average temperature was of 12.9°C during 2008, milder than normal.
• This was a result of five warm months with above average temperatures for the country as a whole and only one with below average temperatures. Temperatures were between 0.5 and 1.0°C above average in the west of the North Island and Nelson, and up to 0.5 °C above average in most other regions.
• Rainfall during the year was 135 percent of normal or more in Wellington and central Marlborough. Only in parts of Fiordland and southern Hawke's Bay were annual rainfall totals 80 percent of normal or less.

Notable climate features in various parts of the country were:

• the economically disastrous drought in the west of the North Island in the first part of the year (estimated costs of at least $1 billion)
• floods in central North Island areas causing loss of life
• damaging floods in July and August in Marlborough and Canterbury
• a significant snow storm in August followed by some unusual late spring snowstorms.

The July and August events have estimated insurance costs of $68 million. By the end of the year, dry conditions had set in over the east of the country.

Of the main centres, Wellington was extremely wet, and Dunedin very sunny and dry.

Over the year, the broad climate setting swayed from La Niña to neutral then back to La Niña. The start of the year was dominated by a significant La Niña event in the equatorial Pacific. This dissipated with neutral conditions during winter and early spring, but weak La Niña conditions redeveloped in the tropical Pacific by the end of the year.

The year in review

Broadly speaking, the picture of the year (with clear geographical exceptions) is:

• January–March: very dry
• April: extremes
• May: cold
• June–August: stormy
• September: more settled
• October–December: becoming dry again

January–March: very dry
In January, heat wave conditions occurred across inland areas of the South Island, and even extended to coastal parts of Canterbury and central Marlborough. Extremely low rainfall occurred in many areas, with monthly totals of less than 10 mm in the Hauraki Plains, Waikato, King Country, coastal Marlborough and parts of north Canterbury. In Waikato it was the driest January in over 100 years of records. The dryness continued through February (50% or less of normal rainfall over much of the North Island from Manukau southwards, and in coastal Otago and parts of Southland) and March (30 to 50% of normal rainfall fell throughout Canterbury, Fiordland, Auckland, Waikato, the King Country and eastern Wairarapa). As a result, severe soil moisture deficits persisted in Waikato, parts of Bay of Plenty, South Taranaki and northern Manawatu, Hawke's Bay, Wairarapa, as well as Marlborough, and parts of south Canterbury, Otago and Southland.

April: extremes
April was a month of extremes with floods in northern New Zealand, while it remained dry in the south. Heavy rainfalls alleviated the severe and significant soil moisture deficits in most of the North Island.

May: cold
May was a cold month, with the national average temperature of 9.6°C being 1.1°C below average. This made it almost 4°C lower than mean air temperatures in April, and the coldest May since 1992.

June–August: stormy
In contrast to May, June was much warmer than average in places especially inland South Canterbury and Otago. The weather got very boisterous in late June, with thunderstorms, hail, lightning and high winds affecting much of the North Island.

July and August were very wet in many parts of the country. In July, rainfall was well above normal (more than 200%) in Marlborough, Canterbury, and eastern Otago, with near record high July totals in many locations. In the last week of July New Zealand was hit by two intense storms which caused flooding, significant damage to property, resulted in several evacuations, and led to the deaths of five people. Rainfall totals were greater than one and a half times their normal values for much of the North Island in August, and Marlborough received over 300% of its normal August rainfall. There were several storms during August bringing a mixture of snow, high winds and heavy rainfall to much of the country. On Mt Ruapehu the recorded 3.5 m of snow pack was the deepest snow base since records began in 1992.

September: more settled
September brought a shift back to much more settled weather conditions for the country. Temperatures were above average for the country as a whole and well above average (more than 1.5°C above their normal values) in South Canterbury and Central Otago. Rainfall in September was below normal for many areas, particularly in parts of Northland, Auckland, Waikato, Coromandel, and the east coast of the North Island where less than 50% of normal rainfall fell.

October–December: becoming dry again
Sunshine totals were well above average for most of the South Island in October, with Dunedin and Balclutha recording their highest October values on record. Rainfall was less than 50% of normal (half) in Otago and coastal south Canterbury and between 50 and 80% of normal in parts of northern Canterbury, West Coast, Tasman, Wellington, Hawke's Bay, Gisborne, Bay of Plenty and Northland.

November and December were sunny months over much of the country and rainfall was once again less than 50% of normal in eastern areas of the country and between 50 and 80% of normal for the majority of the North Island. Soil moisture levels in eastern areas and in Waikato were between 30 and 50 mm lower than normal at the end of December. Double the normal rainfall for November fell in Tasman (mostly in two days) and for December in inland Canterbury and Banks Peninsula.

NIWA analyses of month-by-month records and preliminary end of year data show:

• The highest annual mean temperature recorded for the year was 16.5°C at Leigh.
• The highest recorded extreme temperature of the year occurred in South Canterbury being 34.8 °C recorded at Timaru Airport on 12 January and 19 March and at Waione on 22 January in very hot dry northwesterly conditions.
• The lowest air temperature for the year was -9.5 ºC recorded at Mt. Cook on 20th August.
• The highest recorded wind gust for the year (as archived in the NIWA climate database) was 183 km/h at Mokohinau Island on 11 May in strong easterly conditions, and also 183 km/h at Hicks Bay on 18 June.
• The driest rainfall recording locations were Alexandra in Central Otago with 376mm of rain for the year, followed by Clyde with 378 mm, and then Middlemarch with 386 mm.
• Of the regularly reporting gauges, Cropp River in the Hokitika River catchment recorded the highest rainfall with 10,940 mm, followed by North Egmont 8878 mm for 2008.
• Wellington was by far the wettest main centre with 1662 mm, in contrast Christchurch and Dunedin were the driest of the five main centres with a mere 704 and 705 mm respectively. Auckland received 1226 mm and Hamilton 1220 mm.
• Blenheim was the sunniest centre in 2008, recording 2505 hours, followed by Nelson with 2472 hours, then Lake Tekapo with 2444 hours. Christchurch was the sunniest of the five main centres with 2230 sunshine hours, then Wellington 2205 hours. Auckland recorded 2108 hours, Hamilton 2057 hours and Dunedin 1912 hours.

For more on New Zealand's climate visit: http://www.niwascience.co.nz/ncc/