Mountains can trigger rain.
Mountains pose a significant obstacle to stable air flow. As air approaches the mountain it is forced upwards. At higher altitudes, the temperatures drop, condensing water vapor. This process results in the formation of clouds. Mountains may also restrict or slow down air flow. This restriction may also result in lifting air to high altitudes and creating clouds prior to the air reaching the slopes of the mountain.
As the air is forced higher by the mountain, the clouds that were formed eventually release water in the form of precipitation. This so-called orographic effect occurs because the clouds’ ability to hold moisture lessens as temperatures drop. The higher the mountain, the lower the temperatures at its peak. This forces the clouds to release the precipitation in the form of thunderstorms in the summer and severe snowstorms in the winter. The orographic effect occurs on the windward side — the side that faces the wind.
Sciencing, How Do Mountains Affect Precipitation?, 2018
The upwind side of the mountain receives more rain while the downwind side receives sporadic rain or even dry conditions. However this was portrayed in the Quran 1400 years before it was discovered. The Quran says that higher grounds receive more rain while other grounds receive dew.
[Quran 2:265] And the parable of those who spend their wealth seeking Allah’s approval, and to strengthen their souls, is that of a garden on a high ground, if heavy rain falls on it its produce is doubled and if no heavy rain falls then dew. Allah is seeing of everything you do.
“Rabua رَبْوَةٍ” means high ground. In this verse the higher ground receive more rain while other grounds that didn’t receive rain will receive dew. Today we know why higher ground receive more rain, this is the orographic effect.