The causes of weakness in the heat may include high heat stroke, low blood sugar, and cold and flu. The specific cause should be decided in conjunction with the patient’s other symptoms. 1. Heat stroke: a common cause of weakness in hot weather is heat stroke, which causes a lot of sweating in a hot environment, and may result in headache, fatigue and high fever in mild cases, and dehydration and coma in severe cases. 2. Hypoglycemia: patients with hypoglycemia in the heat of the day may show dizziness, palpitations (rapid heartbeat, often accompanied by panic), fatigue, sweating and so on. 3. Wind-heat colds: weakness in the heat of the day can also be caused by wind-heat colds, often manifested as fever, sore throat, fatigue, pus and runny nose. It is recommended to go to the hospital in time when there is weakness in the heat of the day, to clarify the cause of the disease, and use medication under the guidance of a professional doctor.