Fever in the lower back may be related to the following causes: 1. There may be a local infection. This is often seen in soft tissue trauma or skin-related lesions in the lumbar region, followed by soft tissue infection, which can cause significant local redness, swelling, heat and pain. 2. It may be caused by a herniated lumbar disc. In the process of rheumatism and rheumatoid arthritis attacks, there may be local fever and pain. 4. It may also be caused by old burns, for example, after the occurrence of burns, if they are not treated in time, they often leave a local feeling of obvious hot and painful.