Why is it cooler in the mountains?
Probably you have noticed that it is usually much cooler in the mountains than in nearby lowland places.
This is because the higher up you go, the less air there is above you. The air becomes colder because it cannot absorb as much heat as it is able to hold at sea level.
Perhaps the next thing you discovered is that the climate may be quite different on one side of the mountain from what it is on the other side.
Mountains may block the wind or force it to rise so that it can move over the mountain tops. As the air rises, it also grows colder, and cool air cannot hold as much moisture as warm air. The moisture may be squeezed out in the form of rain or snow.
The wind becomes a dry wind by the time it reaches the other side, with the result that lower country inland may be a dry desert.
Mountains help store water. During the winter months they collect water in the form of snow, which melts in the spring and drains off in rivers and streams. They carry water to places that might otherwise get little or no moisture. – Dick Rogers