Prices lifted 4.9% in this week's GlobalDairyTrade auction, boosted by concerns about supply in the dry conditions.
Fonterra has lowered its forecast milk collection from 1525million kg/ms to 1480million, a 3% drop on last season's collection.
Dry weather in early December significantly affected soil moisture and pasture quality across the country.
While recent wet conditions had helped in some regions, it was unlikely to be enough to bring production back to previously anticipated levels, the co-operative said in its latest Global Dairy Update.
Solid gains were seen in prices for most products, including a 5.1% gain in whole milk powder prices and 6.5% lift in skim milk powder.