Dairy prices have risen for the third successive time at Fonterra's fortnightly GlobalDairyTrade auction.

The GDT price index was up 3.1 per cent and the average price to $US3139 ($NZ4461) per metric tonne on Wednesday morning (NZT).

The important whole milk powder price was up 3.5 per cent to $US2998 per tonne.

The rise follows increases of 1.7 and 1.6 per cent at previous auctions but was below a tipped 5 per cent rise.