Hundreds of trees have fallen, causing damage to properties, blocking roads and disrupting train lines.
Ireland’s Electricity Supply Board said it will take a “significant number of days” to bring back power, while Northern Irish officials warned it could be up to 10 days before all those affected are reconnected.
In Ireland, 625,000 homes and businesses were still without power on Friday evening and around 138,000 people without water.
About 214,000 properties had no power in Northern Ireland, 106,000 in Scotland and 20,000 in north-west England.
Northern Ireland’s infrastructure department said it would take days to assess the storm’s damage, with more than 1,800 fallen trees, branches and other debris blocking roads.
Northern Irish Education Minister Paul Givan said 60 schools had reported “significant damage to some buildings”.
A key focus was identifying schools unable to open on Monday and providing information to parents, he said on X.
“Public services and society has been significantly impacted by the storm that will require a collective and co-ordinated effort in the days ahead to fix,” he added.
While the strongest winds have passed, the storm is still expected to bring gusts of more than 80mph (128km/h) across the coast and hills of Scotland and Northern Ireland.
