A number of homes in Belfast, Bangor and Newtownards have been flooded following torrential rain.
East Belfast was one of the areas worst affected.
Sandbags and plastic flood sheets have been issued to householders whose homes were caught up in the rising waters, while police have urged motorists to take extra care on the roads.
The problems developed after an afternoon of heavy showers.
The Sydenham, Belmont and lower Ravenhill Road areas of Belfast were particularly badly hit.
Belfast Lord Mayor and Alliance MLA Naomi Long said more had to be done to defend the city from flood waters.
Ulster Unionist councillor Michael Copeland said people in the city were now living in fear of rain.
