Summer is always sleepy and weak with physiological factors, there are also disease factors. Physiological factors are common in the high temperature environment of the body a lot of sweat, disease and other factors are mostly seen in respiratory disease and cardiovascular disease. 1. Physiological factors: summer human body is more prone to drowsiness and fatigue symptoms, which has a lot to do with the high temperature and high humidity in the summer, the body is more prone to sweating in the high temperature, which results in the loss of body water and electrolytes. If the replenishment is not timely, the body will cause a feeling of fatigue because of this transient electrolyte disorder. 2. Factors of disease: (1) respiratory diseases: summer is prone to lack of oxygen, especially in the arterial oxygen saturation is insufficient, preferred in the past with chronic obstructive pulmonary disease, bronchodilatation, chronic bronchitis, chronic pulmonary heart disease, pulmonary hypertension, especially in the summer when the air pressure is lower will be respiratory dysfunction, resulting in a lack of oxygen caused by the body of the lack of fatigue and lethargy. (2) cardiovascular disease: in the summer blood viscosity is high, the existence of coronary atherosclerotic heart disease, hypertension, because of the lack of blood supply will also lead to fatigue and drowsiness. In addition, it is also necessary to exclude cervical spondylosis, hypothyroidism and other diseases, so the summer is always sleepy and lethargy need to pay attention to, if it is due to the disease factors caused by sleepiness and lethargy, it is necessary to consult a doctor in a timely manner, under the guidance of the doctor’s systematic treatment.