Rain shadows

https://en.wikipedia.org/wiki/Rain_shadow

Moist air from sea breezes hits mountains, which forces the air upwards, cooling it rapidly and causing rain to form. If the cooling system of the mountains is effective enough, there is little chance of moisture laden air making it very far past the mountains. As a result, a rain shadow forms; on the leeward side of a mountain (the opposite direction to the prevailing winds), there will often be an area where very little rain falls. This explains the dryness of the Sahara desert among many other places.

You can thereby use the direction of a nearby dry area relative to a mountain to infer where the prevailing winds come from. You can use the prevailing wind direction with sufficiently tall hills to find spots for farming with high rainfall. I think you could increase the effectiveness of a mountain's cooling system by increasing the vegetation on it. Be considerate of your downwind farm neighbours when you do this.