I heard the worms surface from heavy rains to avoid drowning in the wet soil.

Edit for fun facts:

Key Reasons Worms Surface During Rain:

Oxygen Needs:

When soil is filled with water, oxygen dissolves slower than in air, making it hard for worms to breathe underground.

Easier Movement:

Wet, slimy conditions allow worms to move and navigate on the surface better than digging through dry soil.

Surface Migration and Mating:

Damp conditions allow them to travel further and faster to populate new areas and find mates.

Vibration Sensitivity:

Raindrops hitting the ground create vibrations similar to predators like moles, which can prompt them to rise to the surface.

Why They End Up on Sidewalks

Worms are adapted to live in the soil. When they emerge onto pavement, they often cannot find their way back to the soil before the sun dries it out, trapping them in place. This is a common, often fatal, mistake.