Emergency services on both sides of the border are this afternoon battling bog, forest and gorse fires.
Fire crews are attempting to contain blazes in parts of counties Donegal, Galway, Mayo and south county Down.
The worst hit is west Donegal, where a number of families were evacuated from their homes in Dungloe and Lettermacaward.
The Donegal fire service say they believe the fire was started deliberately.
Army troops based at Finner Camp have been deployed to assist. A defence force helicopter with a large bucket attached is en route to collect water from Loughanure to try to dampen the flames.
Local MEP Pat the Cope Gallagher said the "inferno" is the worst he has seen in his lifetime, and that the fire services were "stretched to the limit".