Storm Éowyn has broken all-time wind records for Ireland, with gusts of 183km/h at Mace Head, Co Galway.
Gusts of 175.1 km/h or 94.5 knots were recorded in the Port of Galway.
As the full extent of damage is being assessed, more than 715,000 homes and businesses are without power across the State, while 93,000 are without power in the North.
Uisce Éireann says that some 60,000 people are without water due to a lack of power at water treatment plants.
The Aran islands, which were in the eye of the storm, have no power and the mobile phone network is also down, while landlines are still functioning.
Galway Port recorded water levels of 5.25 metres during a surge which only began to recede four hours after high tide, according to harbourmaster Capt Brian Sheridan.
Windows were blown out at Galway Bay Seafoods, and there was some damage to quayside lighting and neighbouring fencing, but there was no flooding, and all ships in the port were safe, he said. The port remains closed until further notice.
Windows were blown out at Galway Bay Seafoods
There has also been damage at Ros-a-Mhil marina, and at least one wind turbine near An Spidéal buckled in half.
Across Galway, many trees were felled, severe damage was done to the roof of Galway Clinic, and up to 70,000 homes and businesses were without power.
In Kerry, two families were evacuated as Storm Éowyn caused severe damage to their homes. One family described how the gable fell out in the house, and gardai advised them to leave.
Donegal’s red alert will remain in place until 1600 hours,while the Connacht counties, along with Cavan, Monaghan, Longford, Louth, Meath, and Westmeath, are under a status orange warning, and the rest of the country has moved to status yellow until 1600.
ESB Networks have advised that their power-check website, PowerCheck.ie, is active but may not be updated until ESB operation teams assess incidents on the ground and again urge patience.
"If you come across fallen wires or damaged electricity network, never, ever touch or approach these as they are LIVE and extremely dangerous,"it says.
ESB Networks asks people to report any damage to electricity infrastructure by calling 1800 372 999.
