Met Éireann has issued another yellow level rainfall and thunder warning to come into effect at 6pm on Sunday evening.
The forecaster said there will be heavy rain with a few thunderstorms which will spread northwards. The warning for the whole country is in place until 3am on Monday morning.
There is also a risk of lightning and spot flooding.
A yellow level thunderstorm warning has also been issued by the UK met office for counties Antrim, Armagh, Down, Tyrone, Derry from 8pm on Sunday until 4am.
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Very heavy rain on Saturday night saw roads in Co Donegal and Dublin city hit by flooding.
The road between Letterkenny and Fintown is closed due to flooding at Glenswilly near the national school, about 10km outside Letterkenny. Footage posted online shows a large stretch of the road flooded and covered in debris and it appears impassable. Adjoining fields are also flooded.
Donegal County Council staff are attending the scene.
Speaking on Highland Radio on Sunday morning, Donegal councillor Donal Kelly said the side of the road had been ripped up along with some pipes.
“The road’s in a mess ... the pipes there are too small and they can’t hold the volume of water. People are furious — it’s not good enough ... I’ve been in contact with the council to have this addressed as a matter of urgency.”
In Dublin, the city council reporting spot flooding at several locations including Portland Place, Seville Place and Merrion Road. There were also reports of flooding on Grand Canal Street on the city’s south side.
The campsites at Electric Picnic were considerably wet and muddy on Sunday morning as a result of the significant rainfall overnight.
Attendees’ legs were covered in mud as they waded through the waterlogged land, as tents that didn’t survive the orange-level weather lay broken on the ground.
Some campers decided to sleep in their cars overnight instead, while others decided to leave early and go home on Sunday morning.
The festival’s main arena held up surprisingly well, remaining largely unaffected by the heavy rain, as festivalgoers prepared for the final day of the annual festival.
Much of the country was under a status orange rainfall warning between 4am and 8am on Sunday. Met Éireann warned that surface and thunder and lightning was possible during that time.