The causes of diarrhea on a rainy day include abdominal cold, gastrointestinal dysfunction and intestinal infection. 1. Cold abdomen: Due to the low temperature on rainy days, when the patient’s warmth measures are not in place, it is easy to cause the abdomen to be cold, the gastrointestinal mucosa is stimulated, triggering the patient to have diarrhea, abdominal pain and other symptoms. 2. Gastrointestinal tract dysfunction: If the patient’s own gastrointestinal tract dysfunction is relatively disordered, when encountered with rainy days, due to heavy moisture, will cause gastrointestinal tract dysfunction, resulting in patients with diarrhea symptoms. 3. Intestinal infections: Due to rainy days, patients are easy to come into contact with unhygienic things, such as rainwater, which causes bacterial infections in the intestinal tract and triggers symptoms such as diarrhea and abdominal pain in patients. If the patient has diarrhea when it rains, it is recommended that the patient go to the hospital in a timely manner to complete the relevant examinations, to clarify the cause of the disease, and comply with the doctor’s instructions for treatment.