Hot, high, and humid weather conditions can change a routine takeoff or landing into an accident in less time than it takes to tell about it. The higher the altitude, the less dense the air. The warmer the air, the less dense it is. Humidity is not generally considered a major factor in density altitude computations because the effect of humidity is related to engine power rather than aerodynamic efficiency. At high ambient temperatures, the atmosphere can retain a high water vapor content.
Density altitude is a crucial criterion that determines the performance capabilities of an aircraft.
As density altitude increases, the molecules of air decrease which means there will be less air flowing over the camber of the wing. The further effects of high temperature and high humidity are cumulative, resulting in an increasingly high density altitude which reduces all aircraft performance parameters. For instance, if the CG is set to the aft position, a stall would be impossible to recover from and may result in a spin. If the CG is set to the forward position, a stall will be encountered in a higher than normal stall airspeed configuration. However, if a pilot becomes complacent regarding aircraft performance or is careless in using the charts, density altitude effects may provide an unexpected element of suspense during takeoff and climb.