The French league had different values at different times: 10 000, 12 000, 13 200 and 14 400 French feet, about 3.25 km to about 4.68 km. It was used for a while together with the metric system but it is not used now. The nautical league was three nautical miles.
Why does precipitation fall mainly on the windward side of a mountain? When humid winds blow from the oceans toward mountains they must rise up to pass over the mountains. The rising warm air cools when it rises and its water vapor condenses, forming clouds rain or snow falls on the windward side of the mountain. microclimate Climate within a small area that differs significantly from the climate of the surrounding area
It means that, on the weather side of the mountain, the air cools down much slower than what it warms up on the leeward side. The result is a dry and warmer air on the leeward side of the mountain. The effect is called a Foehn wind in Europe and a Chinook wind in US and Canada.