Why in mountains gets cold?
We sometimes think that the sun warms up the air but that is wrong. The sunlight warms up the ground and the sea and it is a thin layer of air, right above the surface that then rises because warmer air is less dense. As it does, it climbs into air of lesser pressure and that cools it down by the so-called adiabatic effect. The same happens in your fridge when a compressed coolant is released through a nozzle. And this is why the air is colder as you go up in altitude. The average fall of temperature, a.k.a. the adiabatic lapse rate, is 0.65 C per 100 meter (3 F per 1,000 ft). Note that since cold air is heavier, it tends to fall down during the night, when the sun doesn’t heat the earth. Sometimes, in mountainous regions, this can be felt as a wind that is called a katabatic wind. In places of extreme conditions, like in Greenland where the air from the central glacier falls down in the deep fjords along the coast, that wind can reach gale forces. EDITED: I read Hotzelj answer and hav
