# How Heat Affects Your Body
Heat stress triggers a cascade of physiological responses designed to protect you, but extreme temperatures can overwhelm these safety systems.
When temperatures rise, your body activates its primary cooling mechanism: sweating. Blood vessels near your skin dilate to release heat into the air. Your heart works harder, pumping more blood to the skin's surface. This process demands energy and fluid, which is why dehydration becomes a real concern during heat waves.
Beyond dehydration, sustained heat exposure raises core body temperature. If that temperature climbs above 40.5 degrees Celsius (104.9 degrees Fahrenheit), heat exhaustion sets in. Symptoms include heavy sweating, weakness, dizziness, nausea, and headaches. Without cooling intervention, heat exhaustion can progress to heat stroke, a life-threatening emergency where sweating stops and body temperature spirals dangerously upward.
Heat also stresses your cardiovascular system. Your heart must work overtime to cool your body while maintaining blood pressure and oxygen delivery to vital organs. People with existing heart conditions face heightened risk during heat waves.
Certain populations face greater vulnerability. Older adults have diminished sweating responses and less efficient temperature regulation. Young children struggle to regulate their own body temperature effectively. People taking medications like diuretics or antipsychotics experience altered heat responses. Those with obesity, diabetes, or cardiovascular disease face compounded risks.
Athletes and outdoor workers require particular caution. Intense physical activity in heat multiplies dehydration risk and accelerates the progression from heat exhaustion to heat stroke.
Prevention centers on staying hydrated, limiting time in direct sun, and wearing light-colored, loose-fitting clothing. Electrolyte replacement matters too, especially for prolonged sweating. Monitoring your body for warning signs—excessive fatigue, rapid heartbeat, or confusion