The Ards Blair Mayne leisure centre is being set up as an “emergency support centre” for affected residents and it will be open from 09:00 BST.
The Ulster Unionist councillor told BBC News NI: “This is a very complex and unusual thing to happen.
“It was explained to me that this is only the second of this scale in the UK. Something similar happened in Plymouth.”
Earlier this year, a 500kg (1,102lb) German World War Two bomb forced the evacuation of thousands of people in Plymouth.