Warmer, dry summer set to bake New Zealand

Kiwis could be in for a warmer, drier summer this year - potentially with the weak taste of La Nina.

The National Institute of Water and Atmospheric Research (Niwa) seasonal climate outlook for November to January has predicted temperatures across New Zealand will be above average.

There is a 70 per cent chance of a La Nina pattern over the three-month period.

The ocean-driven climate cycle was characterised by cooler-than-normal sea surface temperatures in the central and eastern Pacific Ocean, near the equator off the west coast of South America.

It was the opposite of an El Nino system, which was typified by warmer sea surface temperatures.

In New Zealand, La Ninas have typically brought moist, rainy conditions to the northeast of the North Island, and reduced rainfall to the south and southwest of the South Island.

Therefore, some areas, such as central Otago and South Canterbury, could experience drought in both El Nino and La Nina.

Warmer than normal temperatures tended to occur over much of the country during La Nina, although there were regional and seasonal exceptions, and Niwa meteorologist Ben Noll pointed out typical conditions weren't guaranteed.

El Nino and La Nina events occurred irregularly, typically every two to seven years, and their strength could vary significantly from phase to phase.

"No La Nina, or El Nino for that matter, is average," he said, adding that the system could prove to be weak and short-lived.

"So while the background might be northeasterly winds, there are likely to be periods through the next three months that are different."

The outlook forecast a 60 to 70 per cent chance of above average temperatures for all regions, with rainfall totals equally likely to be normal or above normal for the north and east of the North Island, and most likely to be near normal in the west of the North Island and the north and east of the South Island.

Rainfall totals for the next three months were equally likely to be below normal or near normal in the west of the South Island.

Soil moisture levels and river flows were also most likely to be below normal in the west and east of the South Island and most likely to be above normal in the east of the North Island.

Niwa meteorologist-forecaster Seth Carrier said northeasterly winds could "pull" moisture from the eastern Pacific, resulting in more rain near the coast, which was why the report predicted "near normal" levels of rainfall for coastal areas.

However, the South Island will be on watch after October was one of the driest months on record.

And the continued dry and hot weather could be "problematic" for agriculture, Carrier said.

Farmers need above-average rain to recover - but that wasn't likely in the next three months.

The official summer outlook will be released next month.