Three people have been confirmed dead in Ireland in incidents related to Storm Ophelia.
Gardai said that a man died in Ravensdale, Dundalk after a car he was in was struck by a tree at around 2.45pm.
A recovery operation is currently under way in the area.
In Cahir, Co Tipperary, a man in his 30s, was killed in a chainsaw accident when he was trying to clear a tree downed by the violent winds.
Earlier, a woman died when a tree fell on to her car in severe winds.
The Garda said the driver was in her mid 50s and was travelling outside Aglish village in Co Waterford when she was killed.
A female passenger, in her 70s, was also injured and taken to Waterford Regional Hospital for treatment, gardai said. Her injuries are not believed to be life-threatening.
Gardai have urged all road users to remain indoors and not to travel unless absolutely necessary.
Gusts of over 96mph (156kph) have already battered the south west coast of Ireland. In Cork, the roof of Cork City’s football stadium was blown off.
Around 360,000 homes and businesses are now without power and trees and power lines have been blown over as the storm makes its way through the Republic of Ireland up into Northern Ireland.
ESB, the Republic of Ireland’s electricity network, warned that more outages are expected and that repairs will take several days.
Ireland’s National Emergency Coordination Group (NECG) on Severe Weather warned that the storm is “unprecedented with serious life- threatening conditions”.
The group added that all unnecessary travel should be avoided.
“Do not be outside during the passing of the storm. The fatality in Waterford emphasises the dangers posed during this period,” NECG added.
Taoiseach Leo Varadkar urged the public to stay safe, saying: “The advice is: stay indoors until the storm passes.
“Whether that is at work, in their home or some other home, stay indoors. Check on neighbours and relatives.
“Bear in mind it is coming your way and it is a national red alert.
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“It is a very dangerous storm. The last time there was a storm this severe 11 lives were lost.”
In the Irish Republic, schools, nurseries and colleges have been closed, court sittings postponed, numerous hospital outpatient appointments cancelled and the Defence Forces put on standby.
Businesses have been urged to consider whether opening would pose a risk to employees.
Schools were also advised to close in Northern Ireland while many college classes were also scrapped. The Lord Chief Justice advised the judiciary to cease all court hearings at 12.30pm.
All government buildings providing non-essential services were closed at 1pm and all non-essential civil service staff were sent home.
Belfast International Airport said the storm is having an impact, with both Ryanair and easyJet cancelling flights. The airport is expecting more cancellations.
Anyone due to travel has been advised to contact their airline.
David Sterling, head of the Northern Ireland Civil Service, admitted that safety advice and information could have been provided more quickly to the public in the region.
There was anger among teachers and parents that the Department of Education did not advise about school closures until late on Sunday night.
Speaking at Stormont prior to an emergency meeting with the permanent secretaries from all Government departments, Mr Sterling said: “Perhaps in hindsight we may have done some things more quickly.
“But now we have given clear evidence and advice out to the community and we will continue to do that.”