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
The Foehn is best known as a southerly wind that occurs when an established southerly airflow approaches the high ground of the Alps. As the air is forced to rise it expands and cools precipitating out its moisture on the windward (southern side) of the mountains. As the air descends the leeward (northern) side it is compressed resulting in a dry, warm turbulent Foehn that can melt snow at a ferocious rate. The Foehn is often a prelude to bad weather approaching from the west.