Fever in adults as soon as the night comes may be caused by viral colds, chronic pyelonephritis and other diseases, when the symptoms appear, go to the hospital for diagnosis. 1. Viral cold: viral cold will appear fever, cough and other symptoms, adults are more distracted during the day, the metabolic rate is faster, the body’s functions are more active, the cold weather in the evening, coupled with the body’s metabolism slows down, leading to the phenomenon of patients have a fever in the evening. 2. Chronic pyelonephritis: often accompanied by persistent or intermittent low-grade fever, loss of appetite, frequent urination, urinary urgency, and regression of urine concentration function. In adults, the metabolizing ability of liver and kidney is weakened at night, and persistent or intermittent low-grade fever is more likely to occur at night. Patients with symptoms of fever at night, should go to the hospital in time to identify the cause of the disease, according to the cause of targeted treatment, daily also pay attention to keep warm, eat a light diet.