Half a million people are expected to make their way to the Phoenix Park this afternoon for a mass celebrated by Pope Francis.
Gardaí are advising anyone heading along to leave the car at home and use public transport.
Mass-goers are being urged to allow time to walk to their designated area from transport hubs and use rest areas provided in the park.
The Pontiff is currently en route to County Mayo where he will visit Knock Shrine and pray the Angelus in front of a crowd of 45,000 people.
Crowds have been gathering at the Shrine since early this morning, with heavy rains failing to dampen spirits.
Pilgrims at Knock Holy Shrine in County Mayo where Pope Francis is due to arrive later this morning, 26-08-2018. Image: Niall Carson/PA Wire/PA Images
Met Éireann has forecast a very wet and windy start to the day - with the heaviest of the rain expected to clear eastwards early this morning.
Suitable footwear is advised given the conditions.
Some items are banned from the park during the event including, large umbrellas, deckchairs, flagpoles and glass bottles as well as selfie sticks.
Meanwhile, a major protest in support of victims of clerical abuse is being held to coincide with the Phoenix Park event.
Organisers of the Stand4Truth event expect thousands to take part – including performers like Hozier, Mary Black and Liam Ó Maonlaí.
The event will also feature spoken word performances by theatre-maker Grace Dyas, poet Sarah Clancy and activist Colm O’Gorman.
It gets get underway at 2:30pm at the Garden of Remembrance in Dublin.
The crowd will walk silently form the Garden to the last remaining Magdalene Laundry at Sean McDermott Street – where marchers will be given the opportunity to leave messages of support for survivors.