Possible causes of sore back of feet on rainy days include overwork, osteoarthritis, rheumatoid arthritis, etc. 1. Overexertion: It may be caused by overwork, such as performing strenuous exercise or participating in heavy physical labor, which causes overwork of the feet, and the symptoms of sore back of the feet may appear. 2. Osteoarthritis: It may be caused by osteoarthritis, which is related to heredity, patient’s age, inflammation, trauma and other factors, resulting in osteoarthritis, whose main symptoms are pain, swelling, limited activities, etc., and may present symptoms of soreness of the back of the foot. And the pain is related to the weather changes, rainy days can aggravate the pain. 3. Rheumatoid arthritis: it may be caused by rheumatoid arthritis, which is related to genetics, autoimmunity, infection, smoking and other factors, and may have symptoms such as soreness of the back of the foot, and rainy days may aggravate the pain symptoms. Soreness of the back of the feet on a rainy day may also have other causes, it is recommended to go to the regular hospital in time to improve the relevant examination, to clarify the cause of the disease, under the guidance of the doctor to carry out targeted treatment or treatment.