WHY do worms crawl out after it rains?

 Biologists once thought that earthworms came to the surface after rain to avoid drowning in their burrows, but this was disproven as the worms breathe through their skin and actually prefer a moist environment. Two theories for their behavior have since emerged:

Ease of migration: Earthworms find it easier to move on a wet surface than to dig through dry soil.

Avoiding predators: Raindrops striking the ground may mimic the vibrations created by predators like moles, and earthworms may come to the surface to escape.