A passive down draft evaporative cooling (PDEC) tower is design to capture the wind at high temperature typically at 40ο C and above the top of tower and cool the outdoor air using water which is allowed to flow through shower and due to evaporation of water out door air gets cooled. Many different types of PDEC exist. This paper explains design of PDEC tower. It is a parallel flow heat exchanger with hot and cold fluid are in direct contact with each other. The wet bulb temperature of air is the lowest possible temperature of the air leaving the tower and entering in air conditioned space. It is suitable in hot dry climate due to large difference between dry and wet bulb temperatures. The mathematical model predicted with the variation of wind speed from 1 m/s to 6 m/s with outside air temperature 35 ο C and relative humidity 20 %, a tower height of 6 m is required.