Q. Why do worms come out when it rains?
A. When people think of worms, they usually mean earthworms, although there are lots of other types. Worms, and earthworms in particular, breathe through their skin. They don't have lungs, though they do have a heart and a circulatory system. When the soil gets waterlogged, there is no longer enough air in the soil for the worm to breathe. It comes to the surface, so it can expose its skin to the air. Worms do need soil that is moist. If their skin is too dry, they also can't breathe.