Homes could be flooded and roads cut off as heavy rain is expected to hit Wales on Friday and last all weekend.
The Met Office has issued a yellow warning of rain and wind covering most of south-east and parts of mid Wales from 03:00 BST until 20:00 on Friday.
A separate warning of rain covering the whole of Wales lasts from 03:00 on Saturday until 18:00 on Sunday.
Homes and business could be flooded and some communities could be "cut off" by flooded roads, the Met Office said.
On Friday, up to 70mm of rain could fall in some areas and winds gusting up to 65mph (105km/h) are possible on the coast.
It covers Blaenau Gwent, Caerphilly, Merthyr Tydfil, Monmouthshire, Neath Port Talbot, Powys, Rhondda Cynon Taf and Torfaen.
On Saturday and Sunday, travel disruption is expected with up to 125 mm of rain possible over high ground.
The warning says there is a "slight chance" of power cuts and loss of other services in some homes and businesses during the bad weather.
"The unusual wind direction associated with the rainfall will mean that the peak rainfall totals are likely to occur in some areas that are usually well-sheltered and drier during unsettled spells of weather," it reads.
"During Sunday the rain will turn more showery in nature and become significantly less widespread."