A major incident was declared in South Wales after "severe and widespread flooding" was brought on by the "devastating" impact of Storm Claudia.
It comes as properties were flooded across Co Wexford overnight and the county remains on alert for the possibility of flooding in Enniscorthy later today.
The storm, named by the Spanish meteorological service, hit Ireland and the UK yesterday and had a "devastating" impact in Wales, where a major incident was declared.
Dozens of people were rescued from their homes or evacuated in the town of Monmouth, in south-east Wales, following severe flooding when the River Monnow burst its banks.
Some 119.6mm of rainfall was recorded at a Natural Resources Wales rain gauge at Tafalog in Gwent, south-east Wales, in the 12 hours to 6am this morning, while 80.6mm was recorded over the same period at Suckley, Worcestershire, the UK Met Office said.
In a statement, the Welsh government said: "Storm Claudia has caused significant flooding in parts of Wales overnight, which continues to affect homes, businesses, transport and energy infrastructure."
Natural Resources Wales (NRW) imposed four severe flood warnings amid fears there may be danger to life.
South Wales Fire and Rescue Service said fast-moving water and blocked routes had created "challenging" conditions.
Gwent Police, Welsh Ambulance Services NHS University Trust (WAST), Sara (Severn Area Rescue Association), Mountain Rescue, the Coastguard, and colleagues from neighbouring fire and rescue services have been involved in the operation.
Peter Fox, the Welsh Conservative Member of the Senedd for Monmouth, described the situation in the area as "extremely bad".
He said: "I personally haven't seen it so bad for probably 40 years, certainly in Monmouth since defences were put in place there.
He added: "The coming days, weeks and months will be very challenging, and I and my office stand ready to help in whatever way we can."
Monmouthshire County Council, which reported a number of road closures, told people to avoid trying to get into town or make unnecessary journeys due to "the severity of the flooding" and the ongoing operation.
National Rail also told passengers in England and Wales to check before they travel as some services could be disrupted.
It comes as Storm Claudia, which brought heavy downpours that battered parts of England and Wales yesterday, is set to be replaced with below-freezing temperatures as a yellow alert for cold weather was issued.
The UK Health Security Agency (UKHSA) issued the cold weather warning for parts of the Midlands and northern England from Monday, and the Environment Agency has warned flooding will continue throughout the weekend.
