Yes, January's weather actually was that bad

Wanganui siblings Grace Forsyth-Farr, 6, and sister Paige Forsyth, 10, endure unseasonable weather on January 19. Photo / File

If you thought summer was missing in action last month, official figures released today prove it.

Nationally, the average temperature last month was 16.4C - that's 0.7C below the 1981-2010 average, and the coldest January since 2014.

And poor Wellingtonians - as well as residents of Palmerston North and Paraparaumu - were short-changed with the least sunniest January on record.

Climate scientists from the National Institute of Water and Atmosphere (Niwa) have blamed the unseasonable weather that many places saw on significantly lower mean sea level pressure than normal over and to the south of New Zealand.

This atmospheric pressure setup caused more southwesterly winds than normal across the country, which encouraged the passage of storms and low temperatures for much of the country throughout the month.

The prevalence of southwesterly winds across the country during January meant that lower-than-average temperatures for the time of year were experienced in many places.

This was especially notable in the west and south of the South Island - including West Coast, Canterbury, Otago, Southland and parts of Tasman - and the west and centre of the North Island, including Waikato and Taranaki, where well-below-average temperatures, -1.2C of the January average, were observed.

Below average temperatures, ranging from minus -1.2C to minus 0.5C of the January average, were experienced in many regions, including western Northland, Waikato, inland Bay of Plenty, Taranaki, Manawatu-Whanganui, Wellington, and parts of the South Island regions that experienced well-below-average temperatures also.

In contrast, areas that were sheltered from the prevailing southwest winds, such as eastern Northland, coastal Bay of Plenty, Hawke's Bay, Gisborne, Marlborough and coastal northern Canterbury, experienced near-average temperatures and a small number of locations in the Hawke's Bay experienced above or well above average temperatures, reaching 1.2C above the average.

Pedestrians struggling against the gale-force wind in central Wellington on January 25. Last month was Wellington's least sunniest on record. Photo / File

The dominant southwesterlies also influenced rainfall patterns across New Zealand in the month, while some intense storms also delivered heavy rain to the South Island and lower North Island.

Much of the South Island, particularly along the West Coast, and in middle and south-coastal Canterbury, Otago and inland Southland, recorded above-normal (120-149 per cent of the January normal) or well-above-normal (149 per cent of the January normal) rainfall.

Parts of the south and west North Island also recorded above-normal or well-above-normal rainfall, particularly in Wellington and Manawatu-Whanganui.

In stark contrast was the east of the North Island, where record low rainfall was experienced.

It was the driest January on record for Gisborne in over 110 years; just 2mm of rain (3 per cent of the January normal) fell - records began there in 1905.

Well-below-normal (less than half of the January normal) or below-normal rainfall (50-79 per cent of the January normal) was recorded at numerous sites across the eastern half of the North Island from Northland through to the southern Hawke's Bay, with only the occasional site in this part of the country receiving near-normal (80-119 per cent of January normal) rainfall.

The pattern of sunshine across the country generally followed the pattern of rainfall.

Western areas of the South Island and southwestern North Island generally recorded below-normal sunshine hours (75-89 per cent of January normal), with a couple of sites recording well-below-normal sunshine.

Wellington, Palmerston North and Paraparaumu recorded their least-sunny January on record.

In contrast, the Far North recorded above-normal sunshine (110-125 per cent of the January normal).

Most sites recorded near normal sunshine for January (90 to 109 per cent of the January normal).

The significant soil moisture deficits in the north and east of the North Island at the end of 2016 continued to worsen in January.

Due to limited rainfall for eastern parts of the North Island during January, soil moisture deficits remained much lower than normal for the time of year.

As of February 1, soil moisture levels were much lower than normal across most of the North Island, particularly in Northland, eastern Waikato, Coromandel, inland Bay of Plenty, East Cape, and Hawke's Bay.

Soils were also drier than normal for coastal northern Canterbury, but wetter than normal for the time of year for Tasman, West Coast, Otago and Southland; near-normal soil moisture levels were observed elsewhere.

January of discontent: By the numbers

• The highest temperature was 33.6C, observed at Hastings on 12 January.
• The lowest temperature was -1.7C, observed at Mt Cook Airport on January 5.
• The highest one-day rainfall was 309mm, recorded at Milford Sound on January 31.
• The highest wind gust was 170 km/h, observed at Cape Turnagain on January 16.
• Of the six main centres in January 2017, Dunedin was the wettest, coldest, and least sunny, Auckland and Tauranga were the driest, and Tauranga was the warmest and sunniest.
• Of the available, regularly reporting sunshine observation sites, the sunniest four locations in 2017 (January 1 - January 31) were Gisborne (315 hours), Whakatane (301 hours), Napier (298 hours) and Kaitaia (286 hours).