When the weather turns cold, it\u2019s natural to shiver when you walk outside. Why do you get goose bumps and curl up when a cold wind blows?\nThe process is called thermoregulation, or temperature regulation, and it\u2019s controlled by your brain. When it gets too hot or too cold, the brain sends signals to the body to get it back to a healthy temperature.\nThe part of the brain that controls thermoregulation is the hypothalamus, an almond-sized area just above the brainstem. When you feel a chilly wind, your hypothalamus can react in several ways:\n\nShivering: Your brain signals your muscles to being shaking rapidly. It targets muscles that surround important organs in your body, such as the heart and lungs. The increased activity in generates heat and actually warms up your body. Once you warm up, the shivering will stop. However, if you\u2019re still cold but no longer shivering, seek help \u2014 if your body becomes too cold, it will stop shivering to conserve energy. This is a sign of hypothermia.\nGoose bumps: When it detects cold, the brain makes the tiny muscles around each hair follicle squeeze together, creating goose bumps. This reaction helps preserve body heat by trapping warm air near the skin.\nCurling up: That urge to hug yourself when you\u2019re cold comes from the hypothalamus, too. By reducing the portion of your body exposed to cold, you can stop as much heat from escaping through your skin.\nGoing pale: Blood flow to your skin is lessened when body temperature drops. That\u2019s because less blood is sent to your skin to avoid coming into contact with cold air, and more blood is being pumped to your organs to keep them functioning.