Niwa is forecasting a warm spring with normal rainfall as being likely over the last quarter of the year.

For the east of the North Island temperatures from October into December are most likely, that's a 50-55 per cent chance, of being above average.

Temperatures in the north and west of the North Island are very likely, that's a 60 per cent chance of being hotter – above average.

October-December rainfall is expected to be about normal for the time of year. There's a 40-45 per cent chance of the rainfall being above normal.

Soil moisture levels and river flows are equally likely to be near normal (40% chance) or above normal (40% chance).

Sea surface temperatures around New Zealand are forecast to remain near or above normal over the next three months.

Despite current borderline La Niña conditions in the tropical Pacific Ocean, and only a modest probability for La Niña to develop by the end of the year, the circulation pattern expected for October-December 2016 for New Zealand is broadly consistent with the typical La Niña signature.

Higher pressure than normal is forecast to the south and southeast of the country, while lower pressures than normal are forecast to the north of the New Zealand. These pressure anomalies are likely to be accompanied with easterly quarter flow anomalies, says NIWA Meteorologist Ben Noll.

El Niño – Southern Oscillation neutral conditions are still present in the tropical Pacific Ocean as a whole, although some indicators are currently in the weak La Niña category.

Sea surface temperatures in the central equatorial Pacific Ocean are near or slightly below average, and slightly above average in the western Pacific and off the South American coast.

The atmospheric conditions over the tropical Pacific are generally consistent with an ENSO-neutral state, but show a leaning towards La Niña, as was already the case last month.

The Southern Oscillation Index is currently positive +1.3, technically in the La Niña category. The trade winds are slightly stronger than normal in the western Pacific. The ocean – atmosphere system in the tropical Pacific shows a mix of ENSO-neutral and weak La Niña signals.

International guidance still slightly favours La Niña conditions over the next three months, but neutral conditions are forecast to become slightly more likely than La Niña by January – March 2017, and the probability for La Niña drops sharply later on. La Niña conditions are only slightly more likely than not over the next 3 months, and become less likely as we progress into the first half of 2017.