Hot north east winds and summer rain for Northland

Expect some rain, wind and high temperatures this summer.

People wanting a heads-up about Northland's summer weather probably don't want to hear wet, windy and wickedly hot.

Expect the typical calling card of La Nina, pushing warm wind and ocean temperatures down from the sub-equatorial Pacific and blowing in — fairly constantly — from the east and north east.

And those conditions make rain.

That is a big part of the picture in Niwa's just-released weather forecast for December until April.

The atmospheric circulation around New Zealand is forecast to be characterised by higher pressure than normal to the south and southeast of the country, and lower pressure than normal to the north, the report said.

''La Nina drives in the humidity, drives in the wind and that creates the moisture in the north,'' Niwa principal forecasting scientist Chris Brandolino said.

The conditions might bring a sigh from holidaymakers planning to camp on the glorious east coast but surfers will just love what will be happening at places like Ahipara on the west coast, he said.

As for the heat, typically temperatures are higher during a La Nina oscillation, and the North is likely to experience heavy humidity over the next few months.

A higher risk of rain could include some major deluges in Northland, and elsewhere in the upper North Island.

That does not mean rain might be constant, day after day, or even for weeks over summer, Mr Brandolino said.

Nor does the wet forecast necessarily mean a huge dampener over the Christmas-New Year period.

The Niwa report does state that in the tropical cyclone season, from November 2017 to April 2018, outlooks indicate the risk for New Zealand is normal or above normal.

That mean a higher risk of at least one ex-tropical cyclone lashing its tail within 550km of New Zealand's coast, Mr Brandolino said. ''And that's a higher risk of rain events, or storm systems that can produce really significant rainfall.''

But the west of the South Island, including Milford Sound, Greymouth, Queenstown and Southland, will have below average rainfall over the summer.

Water temperatures around New Zealand are now above or well above average, and Niwa said this was expected to continue over summer.

The good news is, this La Nina is expected to be in a better mood than usual, and fairly shortlived due to an expected cooling of the sub-equator Pacific Ocean.

But Niwa has warned that depleted soil moisture levels over parts of the country will need to be closely watched.

While Northland and the upper North Island are expected to be wet and warm under largely low pressure systems, Otago, Canterbury and the South Island's southwest will be sunning under high pressure and hot temperatures, with drying winds that could bring the threat of drought.

La Nina and her more laidback boy cousin El Nino — the westerly oscillation— have quite an influence on New Zealand's climate but account for less than 25 per cent of the year-to year variance in seasonal rainfall and temperature at most locations.

At the end of the day, the weather is just weather.