The Met Office has issued a yellow warning of heavy rain for SE Wales which comes into play just after midnight! batten the hatches here as there could be up to 50mm of rain falling on to already-saturated ground!
So, in a little more detail;
This Evening and Tonight: Outbreaks of rain will continue, but should become confined to the south and east, where there will be some heavier, more persistent rain. Cloudy elsewhere with a few showers possible, although largely dry. Winds easing. Minimum Temperature 6 °C.
Wednesday: Rain should clear eastwards early on. Then, a few showers possible in the west but becoming increasingly dry and bright as the day goes on with some sunny spells. Maximum Temperature 12 °C.