The drop in temperature depends on various factors i.e. Air Temperature, % Relative Humidity Level, Room Size, Degree of Insulation & Cross Ventilation. The temperature of air coming out of an evaporative air cooler depends on the temperature and the humidity of the air going in. The constant movement of the air created by the blower – the cooling breeze it creates, makes the occupants of a room feel 4 to 6 degrees cooler than the actual temperature.Evaporative air coolers works best in the hottest time of the day. As the temperature outside increases as the sun climbs, the humidity normally drops. In the early morning, for example, the temperature may be 70 degrees, with a relative humidity of 60 percent. By mid-afternoon, when the temperature has climbed to 90 degrees, the humidity may well have dropped to 30 percent – conditions that make evaporative cooling work more effectively.