Extreme January: Our most sweltering month on record

Monday, 5 February 2018

Temperature at 34 degrees in the shade at Bremner Bay, Lake Wanaka on Sunday January 28 at 6.45pm.

Kiwis sweated through the hottest month on record in January - and the temperatures recorded in a cities-wide breakdown in Niwa's January climate summary are staggering. The institute describes the month using words like 'exceptional', 'profound' and 'unprecedented'.

The average temperatures for widespread parts of the country - Southland, Otago, West Coast, Kapiti Coast and Taranaki - were up to 4 degrees Celsius warmer.

Tahunanui Beach has a fine option for Nelsonians looking to beat the heat this summer.

Most of the country was more than 2C above the January average. Countrywide, the temperature averaged 20.3C for the month. With that figure came record average highs during the days - and hot nights, too.

Specifically, the highest temperature officially recorded was 37.6C at Clyde on January 30. The Central Otago town and neighbour Cromwell had maximum temperatures above 30C for 21 and 20 days, respectively.

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Usually, they'd only have six 30-plus days in an entire year, according to Niwa.

Residents of Auckland's Maraetai say the damage from ex-cyclone Fehi - the second major storm to smash the area this month - is heartbreaking.

That 37.6C day was our hottest since since Darfield reached 38.4°C in January 2004. There were so many record temperature events it's hard to choose which to focus on.

The coldest temperature, 1C, was in Manapouri on January 7.

Record breaking temperatures are set to continue with the days of summer yet to come.

Rainfall was up, too. By a lot, in places.

In the north of the South Island and much of the North Island, it was 120 to 149 per cent above normal and in some areas, more.

Rocks Road Nelson - Cyclone Fehi Aftermath

Takaka got the most rainfall in a single day - 223mm on January 17.

Auckland's North Shore received 275mm rain for the month - higher than the combined rainfall of the previous four months (256 mm from September to December 2017).

Elsewhere, rain was lacking. It was 50 to 79 per cent of the norm or even less than 50 per cent of normal for much of Southland, Otago, and Hawke's Bay.

The highest wind gust was 143 kmh at Mount Kaukau, Wellington.

Meanwhile, Cromwell was the sunniest place in the country with 277 hours of sunshine.

The Niwa summary said the month was characterised by higher than normal sea level pressure to the east of New Zealand, and lower than normal sea level pressure to the west.

That delivered more northerly winds than normal.

Sea surface temperatures in coastal waters and the Tasman Sea remained considerably higher than normal, too.

'The combination of more frequent northerly-quarter winds and higher than normal Sea surface temperatures had a profound influence on air temperatures observed throughout the country during January,' Niwa said.

Rainfall, however, was contrasting.

'The predominant northerly-quarter airflows delivered a steady stream of relatively humid air over the country. This combined with strong daytime heating to cause frequent convective (relatively short-duration, high intensity) rainfall events, particularly over inland parts of the North Island.

'In addition, several low pressure systems brought periods of persistent rainfall, particularly to northeastern parts of the North Island, Nelson and Tasman Districts.'

In comparison, the southern and inland parts of the South Island were 'relatively sheltered from the humid northerly-quarter airflows'.

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