Dr. Universe explains why worms come out when it rains

Washington State University's resident feline scientist, Dr. Universe, answers a question from Courtney of Idaho: Why do worms come out when it rains?

With help from WSU soil scientist Tarah Sullivan, Dr. Universe explores why earthworms sometimes leave their underground homes during rainy weather.

Readers learn that earthworms don't have lungs. Instead, they breathe through their moist skin, absorbing oxygen and releasing carbon dioxide. When heavy rain fills the air pockets in soil with water, worms may head to the surface in search of better breathing conditions.

But avoiding waterlogged soil isn't the only possible explanation. Rainy days also provide cool, damp conditions that allow worms to travel aboveground without drying out, making it easier for them to find new places to live.

The column also highlights the important role earthworms play in keeping soil healthy by breaking down organic matter and recycling nutrients.