Early spring shakes off winter's icy grip

Daffodils are blooming early in Auckland's Cornwall Park. Photo / Brett Phibbs

A cold and early winter has been replaced by an unusually warm and early spring, in a rare act of symmetry by the weather gods.

Forecasters have confirmed what people and plants might already sensed - winter has disappeared long before the official first day of spring.

Spring arrives on Tuesday, but already August looks likely to set records for heat.

Niwa weather data for the first three weeks of the month showed average temperatures about one degree higher than usual for this time of year.

Climate scientist Jim Salinger of the World Meteorological Organisation predicted this month would break the record average temperature of 10C set in 1987 to become the hottest August since records began.

Niwa climate scientist Georgina Griffiths said it seemed as though spring had come early.

Though many would think it only fair to have an early spring to compensate for an early winter, she said the warmth was just a random result of "swings and roundabouts" in natural climate cycles.

Ms Griffiths said northerly winds had warmed the country in the past three weeks.

"August is the time of year when temperatures increase rapidly anyway, but they've really shot up (this year) from being really cold to being a full degree above normal," she said.

"You could say winter came early, finished in July and now we are seeing spring temperatures," Dr Salinger said.

Chilly winter temperatures arrived in the final weeks of May, plunging much of the country into an early cold snap.

May, June and July were all colder than usual, with May setting records for cold average daily temperatures. June was also very cold, while July was closer to normal temperatures at 0.4 degrees colder than the long-term July average of 7.3C.

Ms Griffiths predicted parts of the country would set records for warmth in August, although some places on the East Coast of both islands would be closer to normal. She said Northland, Bay of Plenty and Central Otago were likely to post records or near-records for temperatures.

As of August 25, Central Otago was about 2C hotter than usual, though the last week of August had yet to be counted. Official results for the month will be available in early September.

The forecasters said weather patterns bore most of the signs of an El Nino, but New Zealand was not yet feeling its effects. "We're still in watch mode," said Ms Griffiths. "It wasn't a very typical, wet-with-westerlies winter. There will be more westerlies in spring."

So far Hamilton, Turangi, New Plymouth and Mt Cook looked likely to set records or near-records for low sunshine hours in August.

Kumeu, Wellington and Wairarapa were headed for record or near-record dry months.

Ms Griffiths said the rainfall figures were uncertain as Wellington, for example, looked likely to get more rain in the final days of the month.

Niwa's climate outlook for spring said September would be warmer than average, with temperatures cooling in October and November to bring overall spring temperatures down to about normal levels.

Rainfall is likely to be near normal or below normal.