Altitude at Which Clouds Form On a spring day in the Midwestern United States, the air temperature at the surface is 28.0°C. Puffy cumulus clouds form at an altitude where the air temperature equals the dew point (see Problem 18.89). If the air temperature decreases with altitude at a rate of 0.6 C° /100 m, at approximately what height above the ground will clouds form if the relative humidity at the surface is 35% and 80%? (Hint: Use the table in Problem 18.89.)