The lack of breath in the heat of the day may be caused by heat stroke, asthma, myocardial ischemia and other diseases. 1. Heatstroke: When the body is exposed to high temperature for a long time, it increases the production of its own heat, which is then greater than the heat emitted by the body, and then heatstroke occurs. This is because the patient will experience symptoms such as a drop in blood pressure and an increase in pulse rate, which will lead to a situation where he or she cannot breathe in the heat of the day. 2. Asthma: the main causes of the disease include genetic and environmental factors, pollen, food, paint, temperature changes, air pressure changes and other triggers may trigger asthma, resulting in wheezing, chest tightness, shortness of breath and other symptoms, which can be manifested as the heat of the day do not come up for air. 3. Myocardial ischemia: because the heat will lead to sympathetic nerve excitation, heart rate will be compensatory increase, can aggravate myocardial ischemia, and then chest pain, dyspnea and other symptoms, can also be manifested in the heat of the day do not come to breath. There are many reasons why patients can’t breathe when it’s hot, if the symptoms don’t get better or worsen, you need to go to the hospital to get a clear picture of the cause and follow the doctor’s instructions.