THIRUVANANTHAPURAM: The Central Meteorological Department warned of heavy rains in Kerala. Following this, yellow alert has been sounded in many districts. Yellow alert has been announced in Malappuram, Kozhikode and Wayanad on December 17 and in Kottayam, Ernakulam, Idukki, Malappuram, Kozhikode and Wayand on December 18. Heavy showers have been predicted in isolated places in 24 hours.