As the weather turns cooler, various cardiovascular and cerebrovascular diseases such as angina pectoris enter a period of high incidence. So why does cold cause so much trouble for angina patients? It can be explained according to the principle of thermal expansion and contraction. The principal is true for ordinary objects and also the human blood vessels. When the temperature is relatively high in summer, the blood vessels swell and thicken, the lumen is also enlarged, and the blood flow is easy to unblock. However, when the temperature gradually drops in autumn and winter, the blood vessels will gradually shrink and become thinner, and the lumen will be compressed and become smaller. Patients with arteriosclerosis, due to poor blood vessel elasticity as well as thick tube walls and thin lumens, have slower blood flow speed when the temperature drops. It may turn out that the blood supply of the vascular system of the patient become insufficient, which will damage the vascular endothelium and promote vascular endothelial apoptosis and shedding, resulting in blood vessel embolism, which can be life-threatening. In addition, due to the coldness, human activities are reduced, and the blood perfusion of the brain, myocardium, and internal organs is also reduced. Therefore, when the elderly have insufficient water intake, their blood viscosity rises, increasing vascular resistance and blood pressure, which may cause thrombosis easily, increasing the chance of myocardial infarction and cerebrovascular disease. Therefore, every year when the cold wave suddenly comes and the temperature drops sharply, there will be a sudden increase in patients with cardiovascular and cerebrovascular accidents. While the temperature is gradually dropping, cardiovascular and cerebrovascular patients should pay special attention to cold and warmth, avoid severe cold stimulation, add clothes in time, and take drugs scientifically and on time to protect the vascular endothelium, and do a good job in the primary prevention of cardiovascular and cerebrovascular diseases. Do not get a “heart cold”.