The evaporative cooler can drop the temperature by 25F or more degrees. Evaporation can extract the most heat when the air is dry. So in the dry arid climates of Southwest where relative humidity is less than 30%. Even in the hot humid Southeast, where humidity is 70% or more, evaporative cooling can still drop the air temperature by 5 to 10F. In spot cooling, where evaporated cool air is blowing directly on the people, the air will feel 10 to 15 degrees cooler because of the cooler air will draw more heat from the skin compared to circulation fans which just stir the hot air.