Weather warnings are in place for Ireland and the UK as the newly named Storm Debi is set to bring heavy rain and strong winds.
A handful of locations, including the whole of County Clare, east Galway, south Roscommon, Offaly and Westmeath, are subject to red wind warnings - the highest level possible - for Monday morning.
The Met Office has issued amber alerts for parts of North West England and areas of Northern Ireland throughout Monday.
The storm was officially named by Met Eireann on Sunday morning and this is the earliest in the season that a storm in alphabetical sequence beginning with the letter 'D' has ever hit the British Isles.
The agency warned that from Sunday night there's a risk of "severe and damaging gusts" of wind.
A yellow wind and rain warning is in place for the whole of Ireland today, with Met Eireann warning that it will be "very windy or stormy" amid heavy rain and possible thunderstorms and hail.
The warning finishes at 3pm.
A more severe orange wind warning is in place for 16 Irish counties and covers the period between 2am and midday on Monday.
In the areas where the red warnings are in place, Met Eireann said that there was a "potential danger to life".
An orange warning is in place from 1am to 5pm for the Irish Sea, where southwesterly winds will reach storm force 10.
Meanwhile, the Met Office has issued an amber alert for wind for southeastern Northern Ireland on Monday morning.
The alert, warning of disruption as well as the possibility of flooding of homes and businesses, is in place from 6am until midday.
A yellow warning is also in place for wind and rain across the whole of Northern Ireland from 3am until 2pm on Tuesday.
Yellow warnings for rain and wind have also been issued for the north of England, the Midlands, North Wales and the northeast of Scotland, covering areas including Bangor, Sheffield, Liverpool, and Aberdeen.
Cities, including Blackpool, Preston, and Lancaster, are also covered by an amber warning for wind from 10am to 4pm.
The storm season begins in September and, until now, the earliest 'D' storm named by them was 2015's Storm Desmond, which arrived on 4 December.
The UK and Ireland were also hit by Storm Diana on 28 November 2018, which was named by Portuguese weather service the IPMA.
'In the firing line for wet and windy spells'
Sky News weather forecaster and presenter Kirsty McCabe said: "We've had a very unsettled autumn with a succession of deep low-pressure systems affecting the UK, all thanks to the position and strength of the jet stream.
"This fast-moving ribbon of strong winds high in the atmosphere steers low-pressure systems on the ground, and right now a very strong jet is lying across the south of the British Isles."
Adding that "we're in the firing line for wet and windy spells" on Monday, she continued: "It won't take much more rain to cause further flooding in those areas that suffered during previous storms.
"Until the position of the jet changes or weakens, there could be further low-pressure systems to come this week once Debi moves through."
Storm Debi's arrival comes after parts of Ireland and the UK were devastated by floods during the preceding storms, Babet and Ciaran.
At 7pm UK time on Sunday, the Environment Agency had issued six flood warnings and 74 flood alerts for England and the Scottish Environment Protection Agency had issued alerts for much of the Highland and northeast Scotland and Dumfries and Galloway, where flood warnings were also in place.
The record-breaking Storm Ciaran battered the Channel Islands with hurricane-strength gusts of 104mph just weeks ago, leaving flights to them cancelled.
Areas of Ireland and England also suffered damage, with 10,000 homes in Cornwall being left without power while hundreds of schools were forced to close.