Environment Agency Wales is advising people to be alert as prolonged heavy rainfall could lead to localised flooding across parts of south Wales over the next two days.
Persistent rain is likely to continue this afternoon and overnight into Friday morning.
This may turn quite heavy for long periods over higher ground, particularly across the South Wales Valleys and the Brecon Beacons.
The rain could cause some minor disruption on Friday, with the potential for flooding from drains, ditches and small streams, as well as flooding of roads and low lying land.
Rivers may rise steadily in response to the rainfall which could lead to a small number of flood alerts on rivers in south Wales from Pembrokeshire in the west to Monmouthshire in the east.
The Agency is advising people to take extra care while travelling, as driving conditions could be hazardous.
The rain is forecast to ease and clear from most parts during Saturday.
People are advised to keep an eye on news bulletins and local weather reports for details of any disruption in their area.
For the latest on flood alerts and warnings go to http://www.environment-agency.gov.uk/flood or call Floodline on 0845 988 1188.