Earthworms breathe with wet body walls and breathe oxygen in the air. After the heavy rain, the water overflowed, and the rain squeezed out the oxygen in the gaps in the soil, reducing the oxygen in the soil, so the earthworm could not breathe in the soil. In order to breathe, they drilled out of the ground one by one. After the sun comes out, they should get into the soil in time, otherwise they will die because their bodies are dry and unable to breathe.
So the answer is: because there is too much water in the soil and there is no oxygen, climb out; He died because the sun dried his body surface.