The Met Office has issued a yellow weather warning across Powys for persistent heavy rain.
The weather warning is from 9pm tonight until 5pm tomorrow evening.
Possible power cuts and loss of other services to homes and businesses are expected and they could also flood causing damage to some buildings.
Trains and bus services could be delayed or cancelled and fast flowing or deep floodwater is possible. Road conditions will be poor and some roads may even be closed which could cut off some communities.
The Met Office have said: "Rainfall accumulations through the period are widely expected to be 15-30 mm, but peak totals of 70-90 mm could build up over higher ground.
"In addition, very strong west or southwest winds are expected, producing gusts to 45 mph inland and 60 mph along some coasts and across high ground, with the peak in the winds most likely on Wednesday night."
Wales' Floodline number to call is: 0345 988 1188