Winds were expected to come from the north over spring, combining with higher than average ocean temperatures, resulting in warmer weather.
"As a whole, ocean temperatures are expected to be average or above average.
"Typically if Northland's going to get more rainfall than usual, you tend to have more wind coming from the north."
The amount of rain inmost of Northland for August was normal, but well above average in June.
Northland also had a drier July than most of the country, with 95mm falling in Whangarei - more than 50mm less than normal.
For September to November, Niwa predicted a 40 per cent chance of above average rainfall and a 35 per cent chance of normal rainfall.
"What that means is a drier than normal spring is unlikely," Mr Brandolino said.
Temperatures were likely to be at least 0.5 degrees above average across Northland from September to November, according to the Niwa outlook.
Like Whangarei, Kerikeri and Dargaville were warm over winter, with the third highest average maximum temperature ever recorded in Kerikeri.
Dargaville had the fourth highest overall average ever recorded in winter - 12.5 degrees.
Temperatures across the country were 1.3 degrees higher than normal in August, and average in June and July.
Some parts of the country received multiple heavy downpours, resulting in a far wetter winter than normal.
Canterbury and Otago received around 150 per cent of normal winter rainfall, resulting in widespread flooding.
Wellington and parts of the central North Island also had far higher than normal rainfall over the winter months.
Despite some heavy rain and flooding in the Far North in June, rainfall across the region was close to normal over the winter.
Temperatures August - average, absolute max/min
Whangarei - 12.6, 20.3/2.0
Dargaville - 13.2, 19.1/2.2
Kaitaia - 13.3, 18.8/5.3
Kerikeri - 12.7, 20.2/2.9
Temperatures July - average, absolute max/min
Whangarei - 11.2, 18.4/-0.9
Dargaville - 11.9, 18.0/0.2
Kaitaia - 12.0, 17.1/2.3
Kerikeri - 11.9, 18.2/-0.6
Temperatures June - average, absolute max/min
Whangarei - 12.1, 19.7/0.7
Dargaville - 12.4, 17.7/3.1
Kaitaia - 12.8, 19.3/3.7
Kerikeri - 11.9, 18.2/4.3