Heavy to very heavy rain is likely to occur in the next three or four days in Kerala and Lakshsadweep, the Indian Meteorological Department said on Wednesday.
According to the IMD, a low pressure is likely to form over southeast Arabian sea on October 5 and it is likely to concentrate into a depression and move northwestwards during subsequent 48 hours.
It is likely to intensify into a cyclonic storm thereafter, the bulletin said.
With the depression intensifying, the coastal areas would witness strong winds and fishermen have been advised not to venture into the sea between October 6 and 8.
In the wake of the forecast, an emergency meeting of the Kerala State Disaster Management Authority was held at Thiruvanathapuram to take steps to meet any eventuality.
The state government has decided to take precautionary measures on a 'war-footing', Chief Minister Pinarayi Vijayan told reporters in Thiruvananthapuram after the meeting.
Necessary instructions have been given to district collectors to set up relief camps in hilly areas by October 5 as there is a possibility of landslides and people living in such places should follow the instructions of the officials, the chief minister said.
A red alert has been sounded in three districts of Idukki, Thrissur and Palakkad in Kerala.
People have been asked to avoid night travel in hilly areas and tourists visiting Munnar in Idukki to get a glimpse of 'Neelakurinji', a flower which blooms in the western ghats once in 12 years, should refrain from visiting the place from October 5 until further instructions, he said.
Since there is possibility of floods, people living on the banks of rivers and streams have been asked to move to relief camps.
The government also wanted the central forces to be prepared in view of the alert and said it would seek deployment of five more teams of National Disaster Response Force.
A meeting of the state disaster management authority would be held on Thursday to monitor and take necessary steps on monitoring the water level in dams.
Heavy to very heavy rainfall (12-20 cm in 24 hours) is most likely to occur at one or two places in Kerala from October 4-6 and extremely heavy rainfall (21 cm and above) is most likely to occur at one or two places on October 7, according to the bulletin.
The state had witnessed the fury of the southwest monsoon in August, the worst in the last 100 years, which claimed 493 lives and submerged several districts.
Meanwhile, Deputy Director General of Meteorology (Regional Meteorological Centre) S Balachandran told reporters in Chennai that Tamil Nadu and Puducherry was likely to receive widespread, moderate rain with some isolated incidents of heavy downpour in the next two days.
Fishermen have been advised not to venture into the sea between October 6 and 8 over the South Kerala coast, Lakshadweep area, Comorin area, Southeast Arabian sea and Central Arabian sea, he said.
Forecasting a favourable northeast monsoon, the official had said the state is likely receive rainfall 12 per cent higher than the normal.