"Production is down around the country and it's just a case of buyers and suppliers being a little bit weary."
Mr Cullen said the market was still volatile and, coupled with a lack of rain, the situation for Northland dairy farmers this year could be difficult.
In early December, wholemilk powder prices rose 4.9 per cent to US$3593 a tonne.
In November, Fonterra increased its 2016/17 farmgate milk price by 75 cents to $6/kgMS.
Combined with the forecast earnings per share range of 50c to 60c, the total payout available to Fonterra farmers in the current season is forecast to be $6.50 to $6.60/kgMS before retentions.
A $6/kgMS payout will earn Northland dairy farmers $540 million, $6.50 will rake in $585m, while $6.60 will yield $594m.