Water in the ocean
evaporates, due to the heat of the sun. The
prevailing wind on the British Isles comes from the southwest. We call this a
southwestern wind. The wind blows the moist air against the
mountains. When the moist air climbs, it cools down and there will be
condensation. This will lead to
wet weather on the southwest side of the mountains. The northeastern part of the mountain will stay dry, we call this the
rain shadow.