Worms

Today it rained all day and I got to thinking about worms. You see them all the time when it rains in the summer and their tunnels fill with water forcing them up to the side walk. But what do they do in the winter? I didn't see any worms today so did they go into hibernation? Migrate?

This seems like a question for google. Answer tba.

Apparently they go deeper underground b/c it is warmer, but why don't they suffocate down there? Can anyone answer this?