Endure the storms, then we'll have a nice fine World Cup

September and October will be warmer than usual, and have an average rainfall. Photo / Thinkstock

New Zealand will have warmer than usual weather during the Rugby World Cup, but first must get through a stormy August.

National Institute of Water and Atmospheric Research forecasters are predicting near-average or above-average temperatures in all regions during spring.

Niwa's seasonal climate outlook shows that the tropical Pacific will remain in neutral range - neither La Nino or El Nino - which would lead to a mostly settled, mild spring with a few cold snaps.

Rainfall would also be about average. Auckland, the home base for the World Cup, usually has 17 days of rain in September and 16 rainy days in October.

But that rainfall can be as little as 0.1mm and pass quickly.

Wellington and Dunedin have fewer rainy days, but are 2C to 3C colder than Auckland during spring.

Niwa principal scientist Brett Mullan said sea temperatures remained 0.5C above average after the strong La Nina pattern which ended in May, and this would influence weather until October.

"It's looking settled and warmer than usual," he said.

"Spring generally has westerly days, a little brisk, but with not too much cloud, some nice sunny days.

"I imagine it might be quite pleasant for people touring the country."

But first, we'll have to get through more of the unsettled, stormy weather we had late last month.

Dr Mullan said: "It looks like August might be a bit more stormy. It's nice at the moment, but it's looking like we might get another burst later in the month."

The opening games in the Rugby World Cup tournament, which starts on September 9, are likely to be played in typically erratic spring conditions - intermittent rain and blue skies, with westerly and southwesterly winds.

The weather usually becomes more settled in October, when the knockout rounds of the competition will be played.