There are small patches of unmelted snow in the mountain tops where in never gets warm enough to melt the snow. Underground - Anywhere you go in the world, regardless of how much or little it rains, there is always water underground. After it rains, some of the rainwater evaporates back into the air, but much of it trickles down into the ground and stays there - even in the desert. Since the Andes is a volcanically active mountain range, the magma beneath the ground will heat the groundwater in certain places causing geysers to erupt. Fog and Dew - most of the precipitation that comes to the Atacama is in the form of fog that blows in the from the Pacific.
Fog is essentially very low clouds, consisting of water vapor cooling and beginning to condense.
If you've ever been in fog you know that it can leave you a little moist. When the air temperature reaches dew point the water vapor in the air condenses to leave little droplets of water behind. The few things that are able to survive in the Atacama live on the combined moisture from fog and dew. Many people have the view that deserts are places forsaken by Mother Nature and that no living thing would possibly want to set up camp in a place so dry. Although it is tough to find anything living in the Atacama there are isolated pockets and small patches of plants, which support life for animals and insects.