The Met Office has issued a weather warning of heavy rain for the Amman, Towy, Gwendraeth and Swansea valleys for New Year's Eve.
The yellow warning is from midnight until 9pm.
A spokesperson from The Met Office said: “Heavy rain is expected to bring some surface water flooding and travel disruption.
“Bus and train services will probably be affected with journey times taking longer. Spray and flooding on roads will probably make journey times longer.
“Flooding of a few homes and businesses is likely.”
Outbreaks of rain are also expected across the area on the morning and afternoon of New Year's Day, before dying out.
Some heavy bursts are expected at times, bringing as much as 10mm in an hour, and with the ground already saturated this is likely to result in some surface water flooding and travel disruption.
Natural Resources Wales has also issued a number of flood alerts, meaning flooding is possible, for river catchments across Wales.
The areas affected by the rain warning are Blaenau Gwent, Bridgend, Caerphilly, Cardiff, Carmarthenshire, Merthyr Tydfil, Monmouthshire, Neath Port Talbot, Newport, Powys, Rhondda Cynon Taf, Swansea, Torfaen and Vale of Glamorgan.
⚠️ Yellow weather warning issued ⚠️
— Met Office (@metoffice) December 30, 2022
Heavy rain across parts of southern England and south Wales
New Year's Eve 0000-2100
Latest info 👉 https://t.co/QwDLMfRBfs
Stay #WeatherAware pic.twitter.com/Ow2VP73daD
BBC weather reported: "Saturday will be wet and unsettled, with further outbreaks of heavy rain pushing in from the south-west throughout the day. Staying overcast throughout.
"Sunday will start rather cloudy with frequent showers, these falling heavy at times, but it will turn drier with some late sunny spells in the afternoon. A breezy day.
"Monday will see any cloud dissipate early on, leaving a dry and settled day with plenty of sunshine. Tuesday will see a band of cloud and outbreaks of rain feed in from the west. Turning breezy and milder."
In Wales, the yellow weather warning for rain covers:
- Blaenau Gwent
- Bridgend
- Caerphilly
- Cardiff
- Carmarthenshire
- Merthyr Tydfil
- Monmouthshire
- Neath Port Talbot
- Newport
- Powys
- Rhondda Cynon Taf
- Swansea
- Torfaen
- Vale of Glamorgan
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here