By late spring, most worms are mature. By midsummer, most worms are very young or protected by egg capsules. As the weather cools, young worms emerge. With wet weather, they grow active, making new burrows and eating extra food, resulting in more wormcasts. Egg laying again occurs.
Activity continues as long as soil stays damp.
After a heavy rain, earthworms often appear aboveground. They haven't drowned. You may have seen a bird tugging on an earthworm. Sometimes the worm escapes. A worm crawls by digging tiny bristles into the soil and pulling or stretching forward.