What causes clouds to form on the upwind side of mountain ranges?

Clouds form on the upwind side of mountain ranges due to a process called orographic lift. As moist air approaches the mountains, it is forced to rise, leading to a decrease in pressure and temperature. This cooling causes the moisture in the air to condense into water droplets, forming clouds. The resulting precipitation often occurs on the windward side, while the leeward side may experience drier conditions.