Rainy day calf belly swelling and pain may be due to strenuous exercise and other physiological factors, may also be lower extremity deep vein thrombosis, lumbar intervertebral disc herniation and other causes. 1. Physiological factors: after strenuous exercise, standing for a long time and other reasons lead to calf muscle fatigue, lactic acid accumulation, resulting in calf belly pain. 2. Deep vein thrombosis of the lower limbs: after deep vein thrombosis of the lower limbs, the venous blood return path of the lower limbs is blocked, resulting in the accumulation of blood in the veins of the lower limbs and the passive expansion of the venous walls, which causes distension and pain in the calf belly. 3. Lumbar disc herniation: lumbar disc herniation can lead to sciatic nerve pain when compression of the sciatic nerve, the pain will be radiated to the calf area, resulting in calf swelling and pain. Rainy day calf pain may also be calcium, trauma, inflammation and other reasons, the patient should go to the hospital in a timely manner, improve the examination, clear cause to give targeted treatment.