The Met Office has issued a yellow weather warning for rain over Powys on Thursday 16, March.
Rain is expected on Wednesday evening and will be particularly heavy and persistent overnight into Thursday.
Spray and possible flooding on roads are likely to occur, which will make journey times longer.
40-70 mm of rain is likely, with the wettest spots possibly seeing in excess of 100 mm of rain.
The Met Office's warning impact matrix showing that heavy rain is likely to happen, with a low impact. (Met Office)
There will also be windy conditions, which is likely to further reduce visibility from spray on the roads.
Conditions will gradually improve into Thursday afternoon.