Southern states have been reeling under heavy rains for the past few days, with Tamil Nadu's Chennai and Karnataka's Bengaluru being among the worst-hit cities along with several other areas. The intense rain in parts of south India, particularly Tamil Nadu, is due to the northeast Monsoon that set in on Tuesday and was intensified due to a well marked low pressure area over Bay of Bengal that turned into a depression in the evening that day and crossed coast near Chennai on October 17 morning, as per the India Meteorological Department (IMD).