Complex sentence: The Atlantic squalls pass over the islands, unloading as they collide with the coast, therefore the Cíes receive more or less half of the rain the rest of the Rías Baixas coast receive.
Split into simpler sentences: The Atlantic squalls pass over the islands, unloading as they collide with the coast. Therefore the Cíes receive more or less half of the rain the rest of the Rías Baixas coast receive.