The European Commission has agreed to bring forward 50% of the annual payment to farmers under the Common Agricultural Policy.
Ireland receives €1.8bn annually under the scheme to manage output across dairying, tillage, beef and other sectors.
Steffen Schulz of the EU Office in Dublin said the wet weather had been a major factor in bringing payments forward.
"It's because of the bad weather. Ireland and nine other member states have asked for the advance payments," he said.