More than 370 people have been killed, most of them in landslides, since the monsoon rains started in June.
The Derry families are members of the Derry Kerala Association who had travelled to India to visit family there.
There are around 725,000 people taking refuge in relief camps.
Derry woman Mekha Ann Saji and her father Saji M George were among the group who travelled to Kerala to visit relatives.
She told BBC Radio Foyle they had left on the very day the heaviest of the monsoon rains hit.
“We got out half an hour before the big flood. It was building up but then the major floods all around Kerala struck that day when we left,” she said.
“It was only by luck that we got back here,” she added.
Some 70 families from the southern Indian state of Kerala now live in Derry.
Mekha said the floods had left “around 10 or 12” local families unable to get back to the North of Ireland.
“They went home to visit their families, now they are trapped there.
“The major airport we all use, where all of us get our flights from, is now closed and it is closed until 26 August.”
She said Kerala is a “beautiful state” and that it “was upsetting and scary to watch” the aftermath of the worst flooding in a century.
Her father Saji M George said those left stranded by the devastation are now in a “very difficult situation.”
“People don’t have food or clean water, they don’t have fuel to cook. They are trapped, they cannot move from one place to another.
“We hope it will come to an end soon,” he said.
The relief commissioner of Kerala, PH Kurian, said on Monday that authorities had now rescued more than 200,000 people.Tags: