More than 82,000 people had been rescued on Friday alone, according to the state government.

But on Saturday thousands remained stranded across districts as flood waters from overflowing rivers inundated villages and towns, often rising above the first floor of buildings.

Incessant rains that hit the state over the past week continued in several areas and weather was expected to start improving late on Sunday.

India's monsoon season, between June and September, often sees heavy rains that are vital for agriculture, but which can cause immense destruction.

"Kerala is facing its worst flood in 100 years. 80 dams opened, 324 lives lost and 223,139 people are in 1500+ relief camps," Kerala chief minister Pinarayi Vijayan said on Twitter Friday.

At least 35 deaths were reported on Friday alone.

Prime Minister Narendra Modi carried out an aerial survey of the region on Saturday and announced the federal government would be giving 5 billion rupees ($A98 million) as relief funds to the state.

Vijayan said the situation in Kerala was grave and should be declared a national disaster. He has requested 20 billion rupees of relief funds and estimated the state had suffered a loss so far of 195 billion rupees.

More than 30 helicopters from the armed forces and nearly 400 boats have been involved in rescue operations.

Australian Associated Press