Campsites at Electric Picnic are due to open soon (9am) for tens of thousands of festival fans.
Some 55,000 people will gather at Stradbally Hall in the Laois village.
The advice from gardaí is to ditch the sat nav and follow sign-posted routes from AA Roadwatch to avoid any delays.
Festival PR Lindsay Holmes advised campers to make sure they knew where their tent was itched, adding it could be pitched in a near-empty field, but surrounded by hundreds of others before the day is out.
"Get your bearings there's no fun stumbling around in the dark, trying to find your tent," she advised.
Big name headliners include the XX who play tonight, A Tribe called quest, Duran Duran, Interpol and Chaka Khan.
After his surprise appearance at Reading, many fans are querying whether Drake will turn up at the Picnic.
Organiser Melvin Benn was staying tight-lipped, saying: "Oh gosh, you'd have to ring Drake for that one…I don’t know."