Answer:
Mountains
Step-by-step explanation:
Mountains are colder than the lower elevations. When humid air enters a cooler region, the saturated air begins to cool and this reduces the ability of the air to maintain the evaporated water is the gas state. Molecules of water have reduced enerfy at the cooler temperatures. They will slow down and coalesce with other water molecules to form small droplets of water. The atmoshere cannot hold these heaevier droplets and they begin to fall (i.e., rain).
One migh ask why does the air temperature drop at higher altitudes? Heat rises, so why shouldn't it be warmer on top a mountain, compared to the valley. The reason is that the atmosphere becomes less dense the further from Earth's center on gets. This less dense air has a lower water saturation point, so it rains.