Holiday heat hits in December

December was unusually warm, with many places reaching record temperatures for the month, according to official figures released today.

For the country as a whole, the average temperature during the month was 16.7 degrees Celsius, 1.1C above the 1971-2000 December average, NIWA said in its climate summary for the month.

Temperatures were at least 1.2C above average for the month in much of the North Island, as well as around Nelson and some eastern parts of the South Island. Elsewhere average temperatures were between 0.5C and 1.2C above average.

NIWA climate scientist Dr Andrew Tait said the main reason for the warmth was that the wind had come from the north or northwest more often than normal, bringing warmer air masses from the subtropics.

That happened as anticyclones had tended to park to the east of the country, particularly the North Island.

Tait said that at Christmas ex-Cyclone Evan had brought particularly warm air over the country.

"We're not really sitting in anything like El Nino or La Nina (weather patterns) at the moment," he said.

"It's just that's the way it turned out."

As with the ocean, there were waves of patterns in the atmosphere. Every now and then they could get fixed in a certain pattern for a few weeks.

Places receiving December maximums on Christmas Eve included New Plymouth with 29.9C, Whanganui at 29.5C, Takaka 30.5C, Reefton 32.2C, and Nelson 30.3C, while Paraparaumu equalled the record with 29.2C.

In other areas, the December maximums arrived on Christmas Day, among them Martinborough with 31.3C, Ngawi at 30C, Levin with 29.7C, Wellington with 29.6C, Wallaceville 29.3C, Ohakune 29C, Motueka 31.9C, and Gore with an equal-highest 29C.

Kaikohe reached its December maximum of 28.1C on December 19, Palmerston North hit 30.8C on Boxing Day, the same day as Hawera equalled its December record of 25.5C.

Parts of the country were unusually dry, with less than half the normal December rainfall in Gisborne, Hawke's Bay, Wairarapa, Nelson, and much of Canterbury, Otago and central Southland.

Timaru airport had its second lowest December rainfall total with just 11 millimetres, 21 per cent of normal, while Dunedin airport also had its second-lowest total for the month - a fifth of usual at just 14mm.

It was wetter than usual in the Far North, Fiordland and Stewart Island, with Kaikohe almost double its average rainfall at 217mm, its fourth-highest recorded December total.

Soils were much drier than usual at the end of December in Bay of Plenty, Hawke's Bay, Taranaki, coastal Waikato, Nelson, parts of Canterbury, and central Southland. Soils were wetter than usual in Northland.