Chance of a milder winter for much of North Island

Winter might end up on the warmer side for the north and west of the North Island, in a mixed-bag climate outlook just issued by Niwa.

Temperatures between now and the end of August were forecast to be either near or above average for Auckland, Northland, Waikato, Bay of Plenty, Taranaki, Whanganui, Manawatu, Wellington and the Central North Island.

But further south, across coastal Canterbury and east Otago, the winter was equally likely to be near or below average temperatures.

For everywhere else, temperatures for the next three months likely wouldn't be anything out of the ordinary.

Periodic northeasterly air flows - particularly during the first half of winter - were expected to bring mild periods to northern areas.

But when winds swung to northwesterlies and southwesterlies over the rest of the season, cooler conditions could prevail across southern and western spots.

Rainfall levels were forecast to be near or above normal in the north and east of the North Island, and east of the South Island, but normal or below normal in the west of both islands, and normal in the northern South Island.

"Lower than normal air pressure to the west and north of New Zealand during June may bring a few heavier rain events to the north and east of the North Island and perhaps east of the South Island," Niwa reported.

Soil moisture levels and river flows were expected to be above normal in the north of the North Island, near normal in the east of the North Island and north and west of the South Island, and above or near normal in the west of the North Island and the east of the South Island.

The background picture was El Nino-Southern Oscillation-neutral conditions in the tropical Pacific, which could give way to an El Nino climate system by spring.

In New Zealand, El Nino typically brings cooler, wetter conditions, bringing higher rainfall to regions that are normally wet, and often drought to areas that are usually dry.

But for the short-term, a neutral pattern meant a changeable climate regime.

"At times, southerly quarter flow patterns may deliver sharp cold snaps and snow, although these are likely to be counterbalanced by northerly and/or easterly flow patterns that could deliver some heavy rain events to the northern and eastern North Island and eastern South Island."