system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do earthworms appear in big numbers on sidewalks when it is raining, and why are they not there when it is not raining?

Today was a rainy day, and I saw plenty of earthworms which I rarely see otherwise. This is why I was asking this myself. I also do not see any advantage of earthworms to be on the sidewalks.
gpt
Some will say that the water soaks into the soil and makes it hard for them to breathe, but the more likely reason is that earthworms don't usually move about on the surface because it's so dry that THAT makes it hard for them to breathe.

Worms breathe through their skin and need that skin to be moist. It's easier to move around on the surface than underground, but usually the surface is too dry, so when it rains they can take that opportunity to move around easier and not dry out.