At least 10,000 households have been left with no power and flights have been cancelled as Storm Hannah hit the west coast of Ireland.
ESB Networks said the areas most affected include the Iveragh and Dingle peninsulas and parts of west Cork.
The damage is mainly due to trees falling on overhead lines.
A red weather warning is in place for Counties Clare and Kerry and a separate yellow warning was issued for Northern Ireland.
Irish forecaster Met Éireann said Clare and Kerry could expect gusts up to 95mph (150km/h) on Friday.
The last time a red alert was issued was for ex-hurricane Ophelia in October 2017.
The UK Met Office has said some flooding of homes and traffic disruption could be expected in Northern Ireland.
Southern Wales and south-west England are also expected to be affected.
The Met Office has warned of wind gusts reaching 60-70mph on exposed coastal stretches and 45-55mph inland from Friday evening into Saturday afternoon.
Large waves and spray also likely to affect some coastal routes.
Disruption to road, rail, air and ferry transport are likely, with bus and train services affected.
As the storm moves east across Wales and central England, the heavier rain should clear on Saturday morning with the afternoon slowly becoming drier and brighter from the west.
But it will remain blustery and will feel quite cold in the wind too.