Storm Eleanor poses a ‘risk to life’ as winds reaching 90mph could send debris flying, the Met Office is warning.
Exposed areas are set to suffer the worst conditions as Eleanor hits Northern Ireland before crossing to the western coast of northern England and Scotland.
Tens of thousands of homes and businesses across Ireland have already been hit with a blackout.
Meteorologist Emma Sharples said: ‘There is likely to be some disruption possibly to public transport, bridges and other public services such as mobile phones and people need to be aware that there could be debris as well.’
The Environment Agency warned that strong winds and high tides could bring coastal flooding from Tuesday until Thursday.
A yellow warning of strong winds is in place for most of the UK, while an upgraded amber warning is in effect across northern England, Northern Ireland and south-west Scotland.
The severe warning runs until 4am on Wednesday.
Storm Eleanor is the first named storm of 2018 and the fifth to hit the UK this winter.
In Galway on Ireland’s west coast, streets around the docks were flooded after high tides breached defences and inundated the city.
Water was more than one foot deep in places.
In Wales, people have been advised to keep a safe distance from the sea.
Ceri Jones, from Natural Resources Wales (NRW), said: ‘Large waves could overtop defences and throw up debris – this could easily cause injury or knock you off your feet.’
Pembrokeshire County Council also issued a warning for several areas, including Amroth and Newgale, where overtopping waves could cause disruption.