Nearly three times the monthly average rainfall was recorded in Tauranga in June.
Last month 229mm of rain fell across the city.
The 96mm historic average over the past 10 years.
June last year was also above average with 140mm of rain.
The heavy rainfall was despite Niwa's Seasonal Climate Outlook for May to July stating there would most likely be a near-normal range of rainfall for the Bay of Plenty region, along with the Auckland and Waikato areas, for the month.
Niwa National Climate Centre meteorologist Chris Brandolino said the extra rainfall was due to a combination of north-east winds bringing in warmer temperatures from the sub tropics and warmer ocean temperatures.
"It's one of the reasons why New Zealand and the North Island as a whole has been so darn warm in the month of June, there was a lack of southerlies.
"The ocean temperatures to the east of New Zealand, the sea's surface temperature, were about one degree warmer in some spots than they usually are.
"So air is coming from the sub tropics and on top of that you have air being warmed by the ocean, and that is fuel for rain," he said.
The Bay of Plenty region, including the mid North Island, were the first areas to be affected by the weather for the month. The majority of the rainfall hit during the middle of the month when storms battered the North Island.
Mr Brandolino said Tauranga only had about 80 per cent of the normal amount of sunshine for the June, but the monthly average temperature was higher than average.
Tauranga recorded a high of 19C for the month, one degree higher than the historic average of 18C. The lowest temperature for June was on record with the historic average at 2C.
MetService meteorologist Peter Little said there would be more showers in the Bay of Plenty region over the next few days leading up to the weekend.
There would also be a south-west flow which would bring some colder air up from the South Island but the Bay could be sheltered from its path with warmer temperatures and sunshine expected for some of the weekend.