this is because, as clouds are forced upwards by rising land, they cool and dump their rain. so the side of the mountain facing the ocean (or an inland sea, or a great lake) gets all the rain as the clouds are squeezed out, and the opposite side gets nothing.
my favorite thing is the american great lake snowbelts! so, the 'flow' of weather across north america, in very general terms, blows from the northwest on down south and east to the gulf of mexico.
so the wind is blowing from west to east, and in the winter it's a dryer wind than in the summer because it's colder. but after blowing across a great lake for a hundred miles, the wind is wet again. and that wet turns into snow. so for all of these lakes, the big cities are on the west side, not the east sides, because the east sides absolutely suck to live on.
the sole exception is buffalo, NY, which literally has to be there because, unfortunately, that's where all the important canal stuff between lake ontario and lake erie is happening.
also this always strikes me as cool, check out where cleveland is:
it's right at the edge of that snowbelt. and you see way more cities west of it than east, too.