It does rain in the desert, but not often. One place in the Atacama Desert had no rain for 401 years. In other deserts it may rain every year or once every few years. Rains in a desert may bring a great amount of water to the ground in a short time. Some rain passes straight into the dry soil, but the rest may form a temporary river. Wadis, stream channels that are normally dry, can quickly fill after heavy rain, causing a flash flood. 