The India Meteorological Department has removed a red weather alert from all districts, though some areas are still under water.
India's air force and navy helicopters are airlifting stranded people from rooftops, and dropping food supplies to those they cannot yet reach.
More than 350 people have died in the floods. Thousands remain marooned.
Officials said rescue teams are focused on the riverside town of Chengannur, where as many as 5,000 are feared to be trapped.
A local politician, Saji Cherian, broke down in tears on TV on Friday describing the crisis there. "Please give us a helicopter. I am begging you. Please help me, people in my place will die. Please help us. There is no other solution, people have to be airlifted," he said.
On Sunday, the state's chief minister Pinarayi Vijayan vowed "to save even the last person stranded".