Stormont ministers have held an emergency meeting to discuss the severe flooding across Northern Ireland.
The executive said it would "not be found wanting" after torrential rain caused chaos on Tuesday.
The Fire and Rescue Service received almost 400 emergency calls while NI Water took almost 2,000 calls.
A clean-up operation continued on Wednesday after many spent the night in temporary accommodation. Most of those affected live in east Belfast.
At least seven homes were struck by lightning during the storm.
The deputy chair of the assembly's regional development committee, the DUP's Jim Wells, told Radio Ulster's Nolan Show some houses had been built in areas with a history of flooding.
"This is historical, this is houses built maybe 100 years ago in areas where today they would not be allowed because of the flooding," Mr Wells said.
"Therefore no matter how much money you throw at these problems they're insolvable because of the low-lying nature of the land."
A view from the eighth floor of Clarawood House in east Belfast
Strandtown and Lisnasharragh Primary Schools were closed on Wednesday as a result of the bad weather.
William Duddy from Northern Ireland Water said the extent of the flooding was exceptional and overwhelmed rivers, roads and the sewerage system.
"No sewerage system in the world is designed to cope with the kind of conditions we had yesterday," he said.
More than 30 people were rescued after torrential rain caused widespread flooding in many areas.
Avoniel Leisure Centre was opened to help people affected by the flooding.
Strandtown Primary School and police station were also flooded.
Connswater Shopping Centre had to close after water poured through ceiling vents.
East Belfast was particularly affected by the downpour
About 80 residents at Towell House old people's home on the King's Road in east Belfast had to vacate the building after it was badly damaged by flood water.
Meanwhile, rainwater leaked into the third and fourth floors of Parliament Buildings at Stormont.
Deputy Speaker John Dallat told MLAs the flooding may have damaged the building's fire alarm system causing it to be activated by accident.
Park Road in south Belfast was badly hit
It was also reported that cars were seen floating down Ladas Drive and Channing Street, off the Castlereagh Road.
The Ormeau Road, Annadale Embankment, the Newtownards Road, the Ravenhill Road and the Somerton Road in the north of the city were also affected.
Outside Belfast, the Knockmore Campus of Lisburn Institute had to close after the building became waterlogged.
All classes at the institute have been suspended for the remainder of the week.
Other areas affected were Magherafelt, Omagh, Cookstown and Dungannon.