Why do Earthworms Come Out in the Rain?

It is scientifically proven that earthworms must have moist environment for their existence. Earthworm came out after heavy rains, there are many concepts and myths associated with this action. Earthworms live underground to avoid sunlight as it will drain all moisture from their body. Over exposure of sun can guarantee quick death. Generally it is assumed that earthworms came out on ground after rain due to excess humidity. It is a fact that they need humidity to protect their body from dehydration. It is easier for them to move on moist surface than on dry ground. One theory stresses that they come above the ground for respiratory activities as underground organisms have carbon dioxide. Carbon dioxide increase by rain water and turn into carbonic acid and to avoid a quick death they came out.