Weather services in the UK and Ireland are warning of "potential danger to life" as Hurricane Ophelia makes its way towards western Europe.
The hurricane has been downgraded from a category 3 storm to category 1 and is expected to be an ex-hurricane when it hits southwest Ireland on Monday. Hurricanes do not frequently develop so far eastwards.
In Northern Ireland, all schools are to be closed on Monday.
The Republic of Ireland's counterpart weather service, Met Eireann, issued a wind warning across the country.
The hurricane will have weakened into a storm when it hits the UK on Monday, 30 years after the Great Storm of 1987, in which 18 people were killed. Ireland's most powerful storm on record is Hurricane Debbie in 1961.
Ophelia, on its way from the Azores in the Atlantic Ocean, is blowing winds of 145km/h.
Northern Ireland's Department of Education said the decision to close schools was "entirely precautionary".
All schools and colleges in the Republic of Ireland, where "violent and destructive gusts" are forecast, will also be shut.
Ireland's Taoiseach [prime minister] Leo Varadkar said defence forces were being sent to red weather alert areas - including Wexford, Galway, Mayo, Clare, Cork, Kerry, Limerick and Waterford.
The Met Office said there was a "good chance" Northern Ireland could be hit on Monday afternoon by power cuts, flying debris, large waves in coastal areas and disruption to all travel services.
Three battalions of soldiers are on permanent standby to deal with major incidents in the UK, but the Ministry of Defence said no specific requests had yet been made of them by local authorities.
The Republic of Ireland's Met Office predicts coastal areas will be hit by winds in excess of 130km/h on Monday until Tuesday and is warning against unnecessary travel.