Heavy rain lashed across nine of the 14 districts in Kerala on Tuesday as the Met office forecast that the downpour will continue till Wednesday.
All schools and colleges were closed in the capital district following overnight heavy showers.
A 75-year-old man was electrocuted in Thiruvananthapuram after coming into contact with a live wire.
Idukki district authorities are keeping a close watch on the rising waters in the Idukki dam, where an "orange alert" has been issued as the water level touched 2,395m.
A red alert would be sounded if the waters reach 2,399 metres, paving the way for opening the floodgates of the dam, which have not been opened since 1992.
Even though the catchment areas of the dam have been receiving rains, the intensity is just one-third of what it was earlier. The authorities, however, are confident that there is nothing to worry about.
The residents living in and around the low-lying areas of downstream have already been alerted.
The district authorities have made elaborate arrangements and a 1,000-strong police force is camping in the area to tackle any eventuality.