Power has been restored to thousands of homes after lightning strikes cut electricity supplies to large swathes of the west of the country.
Achill, Co Mayo, was worst affected by blackouts which left about 30,000 homes without power for several hours yesterday and into Christmas Day.
The ESB said a large transformer supplying electricity in the area had been irreparably damaged following a lightning strike.
Scores of homes on the island were without power as families awoke on Christmas Day but repair crews were back working on lines.
Blackouts also affected parts of Clare, Donegal, Galway and Cork.
Elsewhere, Irish Water Safety has warned thousands of Christmas Day charity swimmers nationwide to be aware of the condition "cold shock".
"Cold winter waters can cause 'cold shock' and hypothermia can set in within minutes, overwhelming the fittest of swimmers," it said.
"If sea conditions deteriorate, then the charity swim should be cancelled."
It warned that many participants will not have swum since the summer and the temperature of the water has now dropped considerably.
"It is a fallacy that alcohol will keep you warm when entering the water. In fact, it has the reverse effect and could kill you," it said.