Nationally, the average temperature last month was 16.4C - that's 0.7C below the 1981-2010 average, and the coldest January since 2014.
Until January 29, Dunedin, with an average of 13.4degC, was on track for its second-coldest January, but the average was pushed up to 13.7degC by the end of the month.
Wellingtonians - as well as residents of Palmerston North and Paraparaumu - were also short-changed, having their least sunny January on record.
Climate scientists from the National Institute of Water and Atmosphere (Niwa) have blamed the unseasonable weather on significantly lower mean sea level pressure than normal over and to the south of New Zealand.
The prevalence of southwesterly winds 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 and the west and centre of the North Island.
In contrast, areas that were sheltered from the prevailing southwest winds, such as eastern Northland, coastal Bay of Plenty, Gisborne and Marlborough, experienced near-average temperatures, and some places in Hawke's Bay experienced above or well above average temperatures.
The dominant southwesterlies also influenced rainfall patterns, while some intense storms delivered heavy rain to the South Island and lower North Island.
Much of the South Island, particularly along the West Coast, 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.
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 percent of the January normal) fell - records began there in 1905.
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).
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).
