Why does the higher altitudes feel cooler?

As we go up the temperature decreases, this is normally seen in mountainous places where the temperature is cooler than the plains below.
Actually, there is a simple explanation, as we go up, pressure decreases. The decrease in pressure causes the gases to expand in atmosphere. As the gases expand they lose energy (Joule Thompson effect) and becomes cool.
The same effect is used in refrigeration and Air-Conditioners.