New Zealand experienced extreme temperature swings in 2009, as heat waves in January and early February were followed by the coolest May on record.

Heat waves occurred in January and the start of February; May was the coldest on record; October had its lowest temperatures since 1945; and August was the warmest August ever, according to are port by the New Zealand National Institute of Water and Atmospheric Research (NIWA) released on Wednesday.

In individual months, especially September and November, daily temperatures frequently broke long-standing records, with extremely cold temperatures often occurring within a week or so of record hot events.

NIWA climate scientist James Renwick said in a press release that wild swings in temperature were sometimes only days apart.

Despite it being a particularly snowy winter, Dr Renwick says August was the warmest on record. Auckland recorded a temperature of 25.5 degrees Celsius during the month.

Aoraki/Mt Cook recorded had the highest one-day rainfall in the country of 341 mm on April 27, though Wellington took the crown for being the wettest city overall in 2009.

Nelson, an upper South Island city, was the sunniest city and Christchurch the driest.

Nelson was the sunniest centre in 2009, recording 2571 hours, followed by Tauranga with 2540 hours, then Blenheim with 2477 hours.