Why do earthworms climb out of the ground after rain?

When the oxygen content is lower and lower, the oxygen consumption of earthworms will also decrease. Although they can breathe without oxygen later, the time is quite short, so they will eventually suffocate because there is not enough oxygen. So after the rain, earthworms will be forced to climb out of the surface because the oxygen in the soil and rain is exhausted.

Another reason why earthworms climb out of the surface after continuous heavy rain is related to their excretion. Because earthworms excrete waste in the form of ammonia and urea, they need to be diluted with water. When the environment is dry, earthworms are short of water, and their excretion is bound to be affected. Earthworms do accumulate nitrogen-containing wastes in their bodies under drought conditions, climb to the surface after rainfall, and use rainwater to quickly remove nitrogen-containing wastes from their bodies. In addition, the soil would have combined with nitride, but after soaking in water, the soil would release some nitrogen-containing waste, which would increase the concentration of nitrogen-containing waste in the soil, and earthworms might crawl out of the soil to avoid the increase of nitrogen-containing waste in the soil.