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New Zealand Climate

(borrowed from NIWA)

New Zealand's climate is complex and varies from warm subtropical in the far north to cool temperate climates in the far south, with severe alpine conditions in the mountainous areas.

Mountain chains extending the length of New Zealand provide a barrier for the prevailing westerly winds, dividing the country into dramatically different climate regions. The West Coast of the South Island is the wettest area of New Zealand, whereas the area to the east of the mountains, just over 100 km away, is the driest.

Most areas of New Zealand have between 600 and 1600 mm of rainfall, spread throughout the year with a dry period during the summer. Over the northern and central areas of New Zealand more rainfall falls in winter than in summer, whereas for much of the southern part of New Zealand, winter is the season of least rainfall.

New Zealand Climate zones

New Zealand Climate Maps, click on image to enlarge


Mean annual temperatures range from 10°C in the south to 16°C in the north of New Zealand. The coldest month is usually July and the warmest month is usually January or February. In New Zealand generally there are relatively small variations between summer and winter temperatures, although inland and to the east of the ranges the variation is greater (up to 14°C). Temperatures also drop about 0.7°C for every 100 m of altitude.

Sunshine hours are relatively high in areas that are sheltered from the west and most of New Zealand would have at least 2000 hours annually. The midday summer solar radiation index (UVI) is often very high in most places and can be extreme in northern New Zealand and in mountainous areas. Autumn and spring UVI values can be high in most areas.

Most snow in New Zealand falls in the mountain areas. Snow rarely falls in the coastal areas of the North Island and west of the South Island, although the east and south of the South Island may experience some snow in winter. Frosts can occur anywhere in New Zealand and usually form on cold nights with clear skies and little wind.

See also Auckland Climate and We are upside down

Niwa review of 2010

The country had relatively settled and warm weather last year with Whakatane being the sunniest followed by Nelson and Blenheim, the National Institute for Water and Atmospheric Research (Niwa) said today. Mt Ruapehu, Lake Tekapo and Mt Cook were the coldest. Cheviot had the highest temperature at 35.6degC while Lake Tekapo recorded the lowest at -12.6degC.

Increased anticyclones ('highs') brought relatively settled conditions throughout the country, Niwa said. “The broad climate setting switched from moderate El Nino early in the year to a La Nina by July. “The La Nina had become moderate-to-strong by September.”

Notable climate features included two droughts, several heat waves, and three significant rainfall events, it said. The wettest areas were Cropp River, Doon, and North Egmont with the driest at Clyde, Ranfurly and Alexandra.

The most rain in a single day at 314mm was recorded at Milford Sound on April 25. In the main centres, Tauranga was the sunniest, Wellington the wettest, Christchurch the driest and Auckland the warmest, Niwa said.

Niwa review of NZ weather 2008-2009

(from NZ Herald)

Heatwaves and sudden snow bombarded the country in 2009, a year of extreme heat and cold that left many wondering which season they were in. Last year may have been fairly average by historical standards - ranking just 0.2C below the long-term temperature average of 12.5C - but the annual average masked a topsy-turvy year of sudden temperature change.

The year got off to a dry start in January, with less than half the normal rainfall over much of the country combined with unusually warm temperatures in many places. February kicked off with a heatwave from the 7th to the 12th, and many places topped 34C. But those who thought they were in for a toasty year were due for a shock. Chilly southerly winds plunged temperatures to their coldest in May in many places, with an extra dose of rain on top.

The National Institute of Water and Atmospheric Research's climate summary for the year reveals May was 1.6C colder than the 1971-2000 average for the month (calculated using records from seven long-standing climate stations). The coldest May recorded was in 1913, when the national average temperature was a bone-chilling 2.9C below normal. The early chill ended abruptly in August, which was thehottest nationally at 10.2C since records began 155 years ago.

All regions broke records for average August heat as northwesterly winds delivered an early spring. It was not to last. The coldest October since World War II brought heavy snow dumps to Hawkes Bay and the central North Island and trapped unwary motorists in their cars. “We typically say winter is the months of June, July and August [but in 2009 we said] there was an early onset to winter and spring,” said Niwa climate scientist Dr Andrew Tait. “Unfortunately it got cool again in October, so spring didn't last very long.” Dr Tait said it was relatively common over the past 100 years for winds to get stuck in a particular pattern, as they did in May and August, and deliver an unusually hot or cold month. Last year May and August occurred close together, resulting in an off-kilter year. Dr Tait said the temperature extremes could not be explained by moderate El Nino conditions, which replaced La Nina conditions as the broad climate setting in spring. “Sometimes the weather just happens.”

Meanwhile, Whakatane was again pipped at the post for the title of sunniest town after its annual sunshine could not be calculated because of instrument problems. The Bay of Plenty sun-trap hotly disputed 2008's result, after Niwa questioned the reliability of its sunshine sensor and awarded the gong to Blenheim. Whakatane's 2009 total from May to December (1614 hours) was one hour less than the sunniest town - Nelson - over the same eight months, but figures for the rest of the year could not be calculated.

Of the main centres, Tauranga was the warmest and sunniest, Wellington the wettest, and Christchurch the driest. Auckland was much drier than usual, having 81 per cent of its usual rainfall. It was 0.7C cooler than normal with a mean temperature of 14.6C, and 8 per cent sunnier than average.

Most of the six main centres were slightly colder and sunnier than usual. Wellington was the exception with higher-than-usual rainfall, cooler-than-average temperatures and about average sunshine.

Avalanches became a risk towards winter's end after a long snow season was topped off with hot weather in August.

WEATHER WINNERS

Warmest place: Whangarei, with an average temperature of 15.8°C.

Highest extreme temperature: Culverden in Canterbury with 38°C, Feb 8.

Coldest extreme temperature: -11.7C recorded at Middlemarch, July 19. Strongest wind gust: 184km/h at Southwest Cape, Stewart Island, Nov 4.

Most rain in a single day: Mt Cook with the top three one-day rainfalls - 341mm on April 27, 321mm on May 16 and 295mm on April 26.

Driest place: Ranfurly in Central Otago with 263mm of rainfall. Wettest place: Cropp River in the Hokitika River catchment with 10,956mm.

Wettest main centre: Wellington with 1274mm.

Driest main centre: Christchurch with 589mm.

Sunniest town: Nelson with 2571 hours, followed by Tauranga (the sunniest main centre) with 2540 hours.

Pipped at the post award: Whakatane, whose annual sunshine could not be calculated because of instrument problems. Its eight-month total from May to December (1614 hours) was just one hour less than Nelson's.

NIWA

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