On Saturday, Musari Venkateswarlu, a school teacher in Guntur's Macherla town, said: "I spent the night on my rooftop along with my family after flood water gushed into my house."
More heavy rains were forecast for at least the next 24 hours, the director of a local cyclone warning centre said.
Hundreds of trees were uprooted, electric poles felled and highways flooded as low-lying villages and small towns in the Kurnool and Guntur districts of the Andhra Pradesh state took the full force of the storm.
The dead included 15 people swept away by a flash flood near a bridge construction site in Kurnool, 225km southwest of the state capital, Hyderabad.
About a dozen others were killed by lightning strikes.
Storms and monsoon rains kill hundreds of people and force hundreds of thousands from their homes every year across India.