Dr George Findlay, Cardiff and Vale University Health Board's Clinical Board Director for Children and Women, told ITV News that between six and 12 inches of water had flooded the top two floors of the Children's Hospital for Wales - and some ceiling tiles had come down with the force of the water.
More top news
Catch up with Wednesday's Wales at Six here
Showers will ease and it'll be a dry night for most with clear skies and chilly feeling temperatures.
Hollie Kerrell, 28, was last seen in Knighton on Sunday 22 April. A 35-year-old man has been arrested on suspicion of murder.