Residents have been urged to leave their homes over the threat of a river bursting its banks.
The 34 properties near to the River Wye in Monmouth, Monmouthshire, form part of Riverside Residential Park, but 16 people have said they will stay.
Overnight accommodation is being provided by a multi-agency team.
Natural Resources Wales (NRW) has issued a flood warning for the river and wants those living in the homes to leave before it turns into a rescue.
It said a police officer would stay on site throughout the night to advise anyone trying to return to stay away.
Jo Lee, whose home has been flooded, said: "I was quite frightening because I didn't have any lighting or anything and it was getting quite dark… I didn't like it at all. It unnerved me completely."
Tim England, NRW operations manager said: "Recent heavy rain across south Wales is causing the river level on the Wye in Monmouth to rise and will continue to rise for the next few hours.
"The rain may have subsided, but some river levels are still rising as peaks move downstream."
On Saturday, more than 100mm (4in) of rain fell in 24 hours in some places, according to the Met Office.
Emergency crews rescued people from cars stuck in floods and about 25 homes in Skenfrith, Monmouthshire, were evacuated.
Direct rail services between north and south Wales have also been affected due to flood damage.
In Swansea, the front of a house under development collapsed during the heavy rain.