Storm Ophelia is set to batter Ireland and parts of the UK with "potentially deadly" gusts of up to 80mph from the Atlantic. The UK's Met Office issued an amber warning in Northern Ireland, where all schools are set to close on Monday 16 October.
The Republic of Ireland's meteorological service, known as Met Eireann, extended a "status red" weather alert - its highest - across the entire country. The hurricane has made its way across the Atlantic and is set to hit the UK on Monday, resulting in "exceptional" weather - exactly 30 years after the Great Storm of 1987 killed 18 people across the southeast of Britain.
The Met Office said there is a "potential risk to life and property" in Northern Ireland between 3pm-10pm today and has said there are likely to be problems on the roads with bridge closures, as well as disruption to rail, air and ferry services.
Schools in Northern Ireland have also been advised to close. The Met Office said: "Gusts of 55-65mph are likely across Northern Ireland with 70-80 mph gusts in the far southeast.
"A smaller area of very gusty winds is then likely to run across Northern Ireland from the west with 65-75mph gusts possible for a short period of time in any one location."
A less severe yellow weather warning is in place for much of Wales, Scotland, the North East, North West, South West and the West Midlands from noon to midnight. Heavy rain is also possible in parts of Northern Ireland and western Scotland.
Three battalions of soldiers - 1,200 personnel in total - 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.
In parts of Ireland schools, government buildings and court sittings are due to close, with the weather service warning of potential power cuts, and disruption to transport and mobile phone signals. Dublin and Shannon Airports are advising passengers to check the latest flight information before travelling to the airport. Cork Airport said cancellations are likely.
Ireland's Taoiseach Leo Varadkar said defence forces were being sent to red weather alert areas - including Wexford, Galway, Mayo, Clare, Cork, Kerry, Limerick and Waterford. The decision was taken following a special meeting of the Irish government task force on emergency planning.
Forecasters said Monday would be a "day of huge contrasts" with the strong gusts of wind travelling over the Irish Sea and heading north to central and southern Scotland, sparing eastern parts of the UK.