2017 a year of 'weather extremes' - NIWA

NIWA is calling 2017 a "year of weather extremes" for New Zealand after a series of record-breaking events.

The National Institute of Water and Atmospheric Research released its Annual Climate Summary on Monday morning - which includes everything from droughts to record rainfall.

"Yearly rainfall in 2017 was above normal (120-149 percent of the annual normal) for parts of Auckland, Waikato, Bay of Plenty, coastal Canterbury, and north coastal Otago," NIWA says.

"In contrast, rainfall was below normal (50-79 percent of the annual normal) in much of Southland and interior Otago."

The institute says 2017 was the 5th warmest on record for New Zealand. From November into December, a "marine heatwave" was observed across the Tasman Sea and in New Zealand coastal waters when surface sea temperatures were up to 4degC above average.

For rainfall, 2017 was a year of two halves. The year started off wet and stormy for the South Island in January.

This rainfall spread into the North Island during March and April as a series of ex-tropical cyclones hammered the country, leading to record amounts of rain and flooding for some areas.

However during late 2017 the rain had gone, leading to significant dryness about the South Island and the lower North Island.

"Christchurch observed 1mm of rain during November, the driest November on record," NIWA states.

"By the end of the month, the city had a 35-day dry spell, which increased to 47 days before ending in December."