The warning comes into effect in the early hours of Monday, 1 December, and is expected to remain in place throughout the day, with heavy rain continuing into Tuesday morning.
According to the Met Office, rainfall totals could reach 100–120mm over higher ground, with 60–80mm expected across many hills and 20–40mm at lower levels.
Deputy Chief Forecaster Mike Silverstone said:
“Heavy rain will move over South Wales from late Sunday and through Monday. This is a developing forecast, so it’s important to stay up to date with Met Office warnings in the coming days.”
The warning covers a wide area including Swansea, Bridgend, Cardiff, Merthyr Tydfil, and parts of Carmarthenshire and Pembrokeshire.
Natural Resources Wales has urged residents to prepare for possible flooding, especially with rivers already swollen and ground conditions saturated.
Richard Preece, Duty Tactical Manager at NRW, said:
“We expect to see a number of flood alerts and warnings issued. Surface water issues are also likely. We’re urging people to be vigilant and to make preparations now.”
He added that people should avoid swollen riverbanks and never attempt to walk or drive through floodwaters.
NRW recommends preparing a flood kit with essential documents and medication, moving vehicles to higher ground, and relocating valuable items upstairs.
For the latest flood alerts, residents can visit naturalresources.wales/flooding or call Floodline on 0345 988 1188.
Beyond Monday, forecasters expect a changeable week of weather, with low pressure bringing a mix of rain, showers, and occasional sunny spells.
Recent flooding across Swansea and Carmarthenshire
The Amber warning follows a series of severe flooding incidents across South West Wales in recent weeks.
In Carmarthenshire, a major incident was declared after torrential rain triggered widespread disruption and emergency rescues. Fire crews were called to Glanrhyd Dog Sanctuary near Kidwelly, where 34 animals had to be rescued from rising floodwaters. The sanctuary was left devastated, prompting a community fundraising effort that has since raised over £12,000.
In Swansea, the Cwmbwrla roundabout was once again submerged, causing traffic chaos and highlighting ongoing drainage concerns. Emergency services responded to multiple incidents across the region, with Natural Resources Wales issuing flood alerts and warnings throughout the day.
With saturated ground and swollen rivers, forecasters and emergency planners are urging residents to take precautions ahead of Monday’s expected downpours.
