Why do worms come onto the pavement when it rains?

Question

Why do worms come onto the pavement when it rains?

Answer 1

So thew don't drown.

Answer 2

So they dont drown when the water goes down their holes?

Answer 3

Earthworms only come to the surface when it is moist, when they will not dry out. If their skin dries they can not breathe and then they will suffocate. Usually conditions are best after dark so they are not seen. They come up and move to new regions looking for mates when it is easier to move on warm, moist, spring nights or after a rain on cloudy days. They travel across the top grazing while they seek mates but only when the conditions allow them to survive the trip otherwise the are constrained to this travel within the soil. Since they have no ability to resist drying so they must remain in contact with moist soil at all times.

Earthworms do not drown for several hours underwater living on oxygen they get from the water so it not likely that they are driven out of the soil by usual volumes of rain. Nor do other creatures that require oxygen come to the surface with them. If the soil lacks oxygen for worms it lacks it for the other soil dwelling organisms so they would all appear if that were the reason. Further fall & winter rains bring the water table just as high without bringing worms to the surface.