"Adverse weather, particularly through peak months placed downward pressure on volumes," the co-operative said.
In a separate statement, Fonterra said it had increased its forecast offer volumes for the GlobalDairyTrade by 10,545 tonnes over the next 12 months.
"The changes come in response to Fonterra New Zealand milk collections showing signs of improvement since the unfavourable weather conditions throughout the peak months," it said.
"However drier conditions are persisting across the North Island, including drought conditions in Northland," it said.
A wetter or drier-than-normal late summer and autumn conditions would be a driver of volatility in milk collection volumes, it said.