Earthworms are notorious for appearing en masse after rains, spawning the myth that they actually fall out of the sky with the rain! Trust me, they don't. Apparently, they simply are escaping flooding in their tunnels since they can't withstand long periods of immersion. Of course, in the old days, there wasn't any such thing as asphalt to prevent them from disappearing back into the soil after the rain.
Ken Burton for eNature Naturalists