Maybe the last thing on your mind is an earthworm, but they remind us they're here after a soaking rain.

What You Need To Know

  • Earthworms are more active above ground after rain

  • Scientists have theories about why worms come out when it rains heavily

  • Earthworms are important to the soil ecosystem

After a big rain, you may notice an abundance of worms outside. It seems like they’re everywhere: the road, sidewalk, grass and so on. 

Have you ever wondered why they decide to appear above ground after it rains? Are they looking for food? Did they come above ground looking for a mate?

It turns out there’s no scientifically backed truth about why they appear after it rains. However, there are several theories.

To avoid drowning

Worms don’t have lungs, but they breathe through their skin. They need moisture-enriched soil with a certain oxygen content to survive.

Very wet soil won’t necessarily drown a worm because they can live fully submerged for days if oxygen levels are right. However, according to Penn State Extension, worms can suffocate in soaked soil if conditions are right. So, they move to the surface to avoid that. 

To get around faster

Many scientists agree that worms tend to use soaked soil days as migration days. They can't travel as fast while burrowing tunnels under the ground, and it's too dry above ground on rain-free days for them to survive. 

So, a soaking rain allows them to slither to the surface and move gracefully on the wet ground. 

To get away from a predator that's not really there

Some scientists believe the sound of the rain hitting the ground makes worms think they're in danger of moles. So, they make a bee-line towards the surface as a way of escape. 

Although there are many theories about why worms make an appearance in the rain, we know that worms are very helpful in maintaining soil productivity. Worms help with water infiltration, providing oxygen to plant roots and giving more nutrients to the soil.