"Conditions are favourable for the commencement of northeast monsoon rainfall over Tamilnadu and Kerala and adjoining areas of south Andhra Pradesh and Karnataka around (October) 28," IMD said in a bulletin.
It forecast heavy rain and thundershowers at isolated places over Tamil Nadu on October 28 and heavy rainfall over coastal Andhra Pradesh, Kerala and Andaman Nicobar island the next day.
Northeast monsoon, which is usually active from October to December, brings the bulk of Tamil Nadu's annual rainfall.