Earthworms are permanent inhabitants of the soil. Under what weather conditions can a large number of worms be observed

Earthworms are permanent inhabitants of the soil. Under what weather conditions can a large number of worms be observed on the soil surface? How can this be explained? How are their respiratory organs represented?

1) after heavy rain;
2) the passages of earthworms are filled with water, the oxygen content decreases, the respiration of worms in the soil becomes difficult, and they crawl out to the surface;
3) worms breathe the entire surface of the skin.