The Met Office has issued a yellow 'be aware' warning of heavy rain for parts of Wales.
It says persistent, and at times heavy rain will develop into the early hours of Wednesday, easing later on Wednesday morning.
During this period 15-25 mm of rain is expected widely with totals of 40-60 mm over some hills exposed to the strong southerly winds.
Some intense bursts of rain, as well as autumn leaf fall blocking drains, increase the likelihood of problems.
Areas likely to be affected:
- Blaenau Gwent
- Merthyr Tydfil
- Neath Port Talbot
- Rhondda Cynon Taf
- Vale of Glamorgan
The warning will be in force until 12pm today. The Met Office says flooding of some homes and businesses is likely, along with spray and flooding on the roads, making journey times longer.
Ystrad Road in Fforestfach is closed because of flooding between the B4620 Ffordd Cynore and the B4295 Cwmbach Road (Gypsy Cross).