New Delhi: India Meteorological Department (IMD) has issued a heavy rain alert for Kerala, Karnataka and Tamil Nadu for the next three days.

According to the forecast, active to vigorous monsoon conditions with heavy to extremely heavy rainfall is very likely over isolated places in Kerala, Puducherry, adjoining Western Ghat districts of Tamil Nadu and south-interior Karnataka mainly during July 18-20.

There is a red code warning for Idukki, Malappuram, Pathanamthitta, Kottayam and Ernakulam districts in Kerala.

IMD has also warned fishermen against venturing into the sea especially over the next two days, as strong winds reaching 40-50 kmph are likely along the Kerala coast. High waves in the range of 3.0-3.2 meters are also expected between Pozhiyoor and Kasargod.

The Central Water Commission (CWC) has also issued an advisory on the likelihood of rapid rise in water levels in rivers in Kerala and Karnataka.

Rise in water level is expected in Periyar, Chalakudi, Valapatnam and Kabini basins in Idukki, Ernakulum, Thrissur, Palakkad, Malapuram, Wynadu and Kannur districts of Kerala. In Karnataka, advisory has been issued for basins of Cauvery, Tunga, Bhadra and west flowing rivers like Netravathi.

The rainfall in the catchment areas of the dams on these rivers will help improve water level in the reservoirs.

“But, there are chances of rapid rise in water levels in the downstream of the dams in the river due to precipitation from free catchment for which necessary precautions have to be taken," CWC officials said.

The total live storage available in the 31 main reservoirs in southern peninsula which are monitored by CWC currently stands at 8.51 billion cubic metres (BCM) which is 16% of total live storage capacity of 51.59 BCM of these reservoirs The levels are not only less than the corresponding period last year, but also lower than the average storage of last ten years during the same period.

The southern peninsula is currently facing a high monsoon rain deficit, with up to 59% deficiency in Kerala, Karnataka, Tamil Nadu, Telangana and Andhra Pradesh.

Meanwhile, intensity of rain is decreasing over Bihar and Assam where flood situation has worsened over the last few days.