New Zealand's extreme weather record

File photo / NZ Herald

New Zealand might claim a place in the record books of extreme weather, thanks to a recently rediscovered, 111-year-old reading from Central Otago.

The World Meteorological Organisation (WMO) is considering a report of a -25.6C temperature at Ranfurly on July 17, 1903, which if accepted would become the coldest ever recorded temperature for the Oceania region.

Gregor Macara, a climate scientist at the National Institute of Water and Atmosphere, submitted the reading following a lengthy investigation which included hunting through the newspaper archives of the Otago Daily Times, Southland Times, Tuapeka Times and the Mt Ida Chronicle.

"It wasn't the kind of scientific research I am used to, but I was trying to find out what the weather conditions were in the lead up to this coldest temperature observation," he said.

"Temperatures like this don't occur in isolation in New Zealand, you need a specific sequence of weather events." Mr Macara looked at July news articles and discovered there was a massive snow storm throughout the South Island on July 10, 1903.

In the days immediately following, the skies cleared under a high pressure system and enabled the temperatures to drop drastically.

A report in the Otago Daily Times on July 18, 1903, said the 2.10pm train from Dunedin to Ida Valley could not get beyond Middlemarch, as on arrival at the latter station it was found that no water could be got for the engine, the water in the tanks having been frozen into one solid mass.

Three days later, on July 21 the newspaper reported beef and mutton was frozen and could only be cut with "a saw or chopper, a knife being of no use". Turnips, potatoes and milk were also frozen, and the ink in the post office was in a similar state, the paper reported.

The -25.6?C temperature was recorded at Eweburn Nursery, where a plantation of pine trees had been established, on a form headed "Meteorological Return".

Unfortunately, there was a lack of station information, especially when it came to the instruments used and observation procedures employed, Mr Macara said.

"We can't be 100 per cent certain of the instruments accuracy given there's no indication they were verified at the time, but on the balance of evidence there's no real reason to doubt it did get so cold." The WMO keeps an official, unbiased list of world weather extremes and has a set of procedures to verify and certify records.

It is expected to release its decision on the Ranfurly temperature early in the New Year.

In the meantime, Mr Macara is now working on second report for the WMO, on New Zealand's highest temperature of 42.4C recorded at Rangiora on February 7, 1973.

The WMO presently lists 42.2C recorded at Tuguegarao, Philippines, on 29 April, 1912 as the highest ever recorded Oceania temperature.

Mr Macara said the temperature investigations had been very interesting.

"It is important to maintain reliable records of weather and climate extremes as they can be used as indicators of climate variability and change."

World weather extremes according to WMO official records:

Highest temperature: 56.7c, 10 July, 1913 at Furnace Creek Ranch, California

Lowest temperature: -89.2.c, 21 July, 1983 at Vostok, Antarctica

Greatest 60 minute rainfall: 305mm, 22 June, 1947 at Holt, Missouri Greatest

12-month rainfall: 26.47m, August 1860 to July 1861 at Cherrapunji, India

Heaviest hailstone: 1.02kg, 14 April, 1986 at Gopalganj district, Bangladesh

Maximum wind gust: 407.16km/h, 10 April, 1996 at Barrow Island, Australia