Research work mentioned over here deals with analytic performance evaluation, finding causes of various losses, and providing the solution for improvement of performance in existing conditions of weather. The Natural draft cooling tower of the hyperbolic structure of 210 MW generating unit of NTPC has been chosen for this purpose. Calculations have been made based on observations taken at different intervals of time in different weather conditions. The Range, Approach, Effectiveness, Loss of heat by water, Gain in heat by air, Mass flow rate of air required, etc. have been evaluated and compared with those of designed values. Results and analysis show that the effectiveness of the cooling tower is comparatively higher in winter due to high heat gain in this season. Further, it has been suggested that performance could be increased remarkably by increasing the height of the cooling tower and using eliminators of correct design so that various types of losses could be reduced. (C) 2020 Elsevier Ltd. All rights reserved.