Patients with back pain on rainy days may be caused by rheumatoid arthritis, lumbar intervertebral disc herniation, lumbar muscle strain and other diseases. 1. Rheumatoid arthritis: Rheumatoid arthritis is a kind of allergic disease, its joints localized redness, swelling, heat and pain and other inflammatory manifestations, due to the rainy day cold, damp, may induce the disease aggravate the clinical symptoms, thus appearing the phenomenon of rainy day back pain. 2. Lumbar intervertebral disc herniation: in patients with lumbar intervertebral disc herniation, nerve root compression is the main cause of lumbar and leg pain, and on rainy days, due to the humid environment and decreasing temperature, it leads to lumbar muscle contraction and spasms, which aggravates the stimulation of the dural sacs and nerve roots, and aggravates the clinical symptoms, and thus, lumbar pain aggravated by rainy days occurs. 3. lumbar muscle strain disease: lumbar muscle strain, also known as functional lumbago, refers to the lumbar muscles and their surrounding fascia, periosteum, chronic injury inflammation, mainly manifested as lumbar or lumbosacral distension, soreness, etc., the rainy day humidity and cold will also induce lumbar muscle contraction and aggravate the clinical symptoms. Rainy day back pain may be caused by other reasons, it is recommended that the patient timely medical examination, clear cause for targeted treatment.