Three people have died in storm-related incidents in Louth, Tipperary and Waterford.
The first fatality caused by storm Ophelia was a woman in her 50s who died when a tree fell on the car she was driving in Co Waterford yesterday morning.
She has been named as Clare O'Neill, from Aglish. Ms O'Neill, who worked as a cancer support coordinator, was due to celebrate her 59th birthday today.
The incident happened on the R671 near the village of Aglish at 11.40am.
A woman passenger in her 70s was taken to University Hospital Waterford with non-life threatening injuries.
A 31-year-old man died while in the course of clearing a fallen tree in Co Tipperary.
He has been named as Michael Pyke from Ardfinnan.
Mr Pyke sustained the fatal injury while clearing a fallen tree at Ballybrado, Cahir at about 12.30pm.
His body has been removed to Clonmel Hospital.
Mr Pyke was an electrical apprentice student at Limerick Institute of Technology, where he was currently in phase six of his training.
Flags are flying at half mast at LIT and a book of condolence has been opened.
Another man in his 30s died in Co Louth. He has been named locally as Fintan Goss.
It is understood he was driving home along the old Dundalk to Newry road when his car hit a fallen tree at Ravensdale shortly after 2pm.
Taoiseach Leo Varadkar said the condolences of the country and the Government go to the families of those who have lost their lives.
"The most important thing is to make sure that nobody else loses their life and I would plead with people to put safety first.
"The storm will pass by midnight tonight but in the meantime everyone needs to put safety first and bear in mind that even if the storm has passed there are still dangers; trees on the road, live power lines."
Mr Varadkar has also spoken to British Prime Minister Theresa May.
A Downing Street spokesman said: "On Storm Ophelia, the Prime Minister expressed her sympathies for the loss of life and said the UK government stood ready to provide any support if requested."
Advice from Government remains to stay indoors as the storm passes over Ireland.