The Indian Meteorological Department has warned of heavy to very heavy rainfall’ in isolated places of Kerala on October 4, 5 and 6. The depression off the Sri Lankan coast may turn into a low-intensity cyclone, IMD said in its all-India weather warning bulletin released on Wednesday. The three districts - Idukki, Thrissur and Palakkad - located on the northern and central part of the state are more likely to be hit by the rainfall.