Why are the mountains cooler than the valleys?

That often happens. But generally air is cooler at high altitude because of so-called adiabatic cooling. The air expands as it rises because pressure is less, and cools in the process. Sinking air can compress and warm. read more

That often happens. But generally air is cooler at high altitude because of so-called adiabatic cooling. The air expands as it rises because pressure is less, and cools in the process. read more

"Air however is not a great conductor of heat, so the further you move away from the Earth's surface the cooler the air will get," he says. So while hot air does rise because it is less dense than cooler air, it will lose this extra heat quite quickly. Scientists call this the environmental lapse rate. read more