Environment Agency Wales has urged people in South East Wales to be vigilant as a band of heavy and intense rain is expected overnight and into Thursday.
There is the potential for localised surface water flooding, and Flood Alerts and Warnings could be issued for some rivers in the area.
The band of heavy rainfall will spread across most of Wales on Thursday with the worst of the weather concentrated in the South East.
However people living in mid and west Wales are also urged to be vigilant today and Thursday as the rain continues overnight. Flood Alerts could again be issued for some rivers in all of these areas.
With land remaining saturated from recent heavy rainfall, any further rain could quickly find its way into rivers and streams.
Flood Alerts and Warnings could be issued for some rivers in these areas.
There is also a risk of localised flooding of roads and low lying land from blocked drains, ditches and small streams.
Agency officers are currently working in the area to check that rivers are clear of blockages and that Agency defences are in good working order.
People are advised to take extra care while travelling as driving conditions could be hazardous.
Flood water is extremely dangerous and people should not attempt to walk or drive through flood water.
The Agency is advising people to keep up to date with the latest information in their area by listening to local weather and traffic reports, and viewing the latest information on the Met Office website