Calculations of data from seven weather stations by independent climate scientist Dr Jim Salinger showed last month's mean temperature came in at 10.3C making it the warmest ever.
When factoring in 24 stations across the country, the results were 9.8C making it warmest equal with 2003.
Dr Salinger said his figures had shown several towns and cities, including Tauranga, Kaitaia, Masterton and Hokitika, had their warmest June, while Auckland enjoyed its sixth warmest.
The warm month had been put down to a lack of southerly winds, with the equatorial Pacific Ocean remaining in a neutral ENSO-state - meaning it was influenced by neither El Nino nor La Nina patterns.
"When you have a neutral weather pattern, everything gets thrown at you, but generally speaking, we are in a warmer trend," said analyst Philip Duncan of Weatherwatch. "We are not really seeing a prolonged period of southerlies - we are having prolonged periods of subtropical and Tasman sea air flows - and that's the sole reason why it's so warm."
Dr Salinger said New Zealand was tracking at 0.4C above average for the first half of the year, and the warm trend showed no signs of changing over the coming months. But according to Niwa's outlook, that didn't mean winter would also be wetter.
Rainfall is predicted to be either normal or below normal for the west of the North Island and north of the South Island, and near normal for the rest of the country.
Soil moisture levels were expected to be either normal or above normal in the north and east of the North Island and east of the South Island, and equally likely to be normal in the west of the North Island and the north of the South Island.
The month that was
The skifield manager
A "lean season" for snow postponed skiing on Mt Hutt by nearly a week last month - but James McKenzie considered himself better off than snow-starved ski area managers elsewhere. The mountain may have seemed to visitors a bit more rocky than its usual well-covered winter appearance, but "some of the other ski areas are now into several weeks' delayed opening".
The farmer
For farmers on the South Island's West Coast, June had been "exceptionally warm", Hokitika dairy farmer Andy Thompson said. The month had also been a sodden one for pastures in the area - with flash flooding and close to 500ml rainfall in some areas near the mountains - constantly causing farmers to move stock on to stand-off pads to protect soils.
The fire chief
Up until June, the year had been relatively quiet for the Whitianga Volunteer Fire Brigade. "Then it just went berserk - we had everything," brigade chief Merv George said. One of the big windy, wet storms, on June 11, sent roofs flying from homes, toppled trees and knocked over signposts. "I can't remember being out in wind like that before, and I've been here all of my life."
