Farmers have welcomed the higher-than-average rainfall recorded last month but warn milk production is down in the Bay and further dry spells could spark a drought.
Bay of Plenty Rural Support Trust chairman Derek Spratt said wetter December conditions had "lifted farmers spirits unbelievably" although Niwa had predicted a period of La Nina.
"So yeah, we have just got our fingers crossed at the moment. Last year was fantastic for the coastal Bay of Plenty because the rain came in at the right time and growing conditions were great ... but a presentation from Niwa showed in early December moisture content levels were 50 per cent below average.
"That was how dry we were, going back to what we were like in 2011 before the big drought came in."
October and November had been dry and traditionally February was the month to watch, he said.
"I am due to report to the Ministry of Primary Industries and I will be saying currently conditions are normal and if we get follow-up rains in January and February things could be okay."
Quite a few farmers had made early supplements and already fed out, he said.
"Production is down ... the grass wasn't growing fast enough for the intake of cows so they have had to feed that out."
Some farmers had palm kernel contracts but the lower milk payout also meant some were pulling out of maize contracts on crops due to be harvested in March.
"It is having an effect right throughout. We don't want another dry spell on top of the forecasted payout because there will be farmers struggling."
Niwa climate scientist Nava Fedaeff said the total December rainfall for Tauranga was 145.mm or 153 per cent.
"This is considered to be well above normal."
Total rainfall for 2014 was 1010mm and within a 20 per cent range of the normal rainfall of 1189mm.
Data from Niwa's Hotspot Watch on December 19 showed the western parts of the Bay of Plenty region were experiencing severely dry soils.
On January 5, the soil deficit in the region ranged from -50mm to - 90mm and the only rain recorded in Tauranga in the last week was over New Year's Eve when 4mm fell. Meanwhile, the average temperature recorded in 2013 for January was 19.8C and 19C in January 2014 compared with a 20.6C average for the first four days of January.
New Zealand Dairy Statistics show in 2013/14 the country's 4.92 million cows achieved a new season record in milk production, surpassing 20 billion litres. The milk contained 1.83 billion kilograms of milk solids, worth $15.5 billion with the season's $8.47 average dairy payout.
The Bay of Plenty also tracked 8 per cent higher in milk production over the same time frames.
DairyNZ senior economist Matthew Newman said the past season's record milk production and prices had helped put farmers in a better position to cope with the rapid decline in milk prices this season.
Across the country, the national herd grew by 138,600 cows (2.9 per cent) and production from each cow was up 7.2 per cent. Genetic merit also improved, with the average cow's breeding worth and production worth increasing 14 per cent and 10 per cent respectively.
LIC commercialisation and industry relations manager Steve Harcourt said statistics confirmed the progressive attitudes of New Zealand dairy farmers and the value of good genetics to improve productivity.