A February which produced heatwaves and tropical cyclones has been confirmed as the hottest on record for Auckland and Nelson.

Despite a cooler final week of summer, all of the North Island was 1.2C hotter than its mean temperature in February, and Tauranga was 2.2C warmer than normal.

National Institute of Water and Atmospheric Research climate scientist Georgina Griffiths said last month was a tale of two islands.

While the North Island sweltered in dry, hot conditions, the South Island had record rainfall in usually arid Alexandra.

Auckland had its warmest February, with an average afternoon temperature of 25.8C at the Leigh monitoring station.

Nelson, with a reading of 24.2C, also had its hottest February in nearly 50 years of record-keeping.

Barely a drop of rain fell in central North Island last month.

Taupo and Ohakune had only 2mm of rainfall. In a usual February, Taupo would get 90mm of rain.

But the usually bone-dry Central Otago had twice as much rain as a normal February.

The small amount of rainfall in the North Island meant soil moisture levels were deficient in usually damp areas - Wairarapa, Taranaki and even Wellington.

A soil moisture deficit of more than 110mm was also evident in Nelson, Marlborough and north Canterbury.

During the heatwave from February 2 to 7, several towns had their hottest day on record. Timaru's reading of 41.3C was its warmest in 125 years and only 1.1C shy of New Zealand's hottest day.

The abnormally high temperatures also encouraged many unwanted phenomena - greater numbers of microscopic jellyfish in Auckland's warm waters, an increased threat of large storms, more swarms of household flies, and an outbreak of avian botulism in urban waterways.

Auckland Regional Public Health issued a warning in mid-February on the dangers of excessive heat, and urged people to keep an eye on the most vulnerable - elderly, young people, and those with medical conditions.

Niwa predicted a mild autumn in all parts of the country as the warmer La Nina temperatures faded before winter.

* All of North Island 1.2C warmer than usual.
* Tauranga - mean temperature of 21.7C (98-year record).
* Auckland's mean maximum temperature 25.8C.
* Heatwave from Feb 2 to 7.
* Taupo, Ohakune - 2mm of rain (3 per cent of usual rainfall).
* Soil moisture deficits in Wairarapa, Taranaki, Manawatu and Kapiti Coast.
* Highest peak temperatures on record in Timaru (41.3C), Gisborne (36.2C) and Te Puke (31.2C).