This paper discusses the distribution of temperature around the condenser outfall of a nuclear power plant, Madras Atomic Power Station (MAPS) located 60 km south of Madras. The distribution of temperature is strongly influenced by the seasonally reversing coastal currents at this location. The thermal plume moves to the north hugging the coast when the currents are northerly during the southwest monsoon period (June - September) and moves to the south when the currents are southerly during the northeast monsoon period (October-February). There are also situations, particularly during the transition from northeast to southwest monsoon, when the thermal plume showed a movement towards the intake resulting in recirculation of heated effluents. It is observed that following the commencement of station operation there has been a general warning up of coastal waters resulting in an increase in temperature of about 1° C in April / May and 2" C in June / July. The paper makes an assessment of the significance of the observed temperatures in the context of power plant operation and ecology of coastal waters.