Significant flash flooding hit parts of Welshpool on Sunday morning.
Welshpool Hospital was forced to close its birth centre and temporarily relocate its minor injuries unit.
People were advised to avoid the town centre, especially Salop Road.
Mid Wales Fire and Rescue Service says the flooding was mostly on the road but it has caused some damage to a number of properties in the area, including the hospital and a school.
Powys Teaching Health Board says the main ward at Welshpool Hospital remained unaffected and patients continued to be treated as normal.