Annual Probability of Heat-Related Illness Requiring ER Visit

The CDC estimates approximately 67,000 emergency room visits for heat-related illness occur in the United States each year. Heat-related deaths average about 700 per year, though this figure is likely underreported. Extreme heat is the deadliest weather phenomenon in the US, killing more people than hurricanes, tornadoes, floods, and lightning combined.

Heat-related illness ranges from mild heat cramps and heat exhaustion to life-threatening heatstroke. Heatstroke occurs when the body's core temperature rises above 104 degrees F and the body's cooling mechanisms fail. Without rapid treatment, heatstroke has a mortality rate of up to 80%; with prompt cooling, survival rates improve to about 90%.

Risk factors include age (children under 4 and adults over 65 are most vulnerable), outdoor workers (construction, agriculture, delivery), athletes, people without air conditioning, those taking certain medications (diuretics, beta-blockers, antipsychotics), and people with chronic illnesses. Climate change is increasing the frequency and intensity of heat waves. Prevention includes staying hydrated, avoiding strenuous activity during peak heat, using air conditioning, wearing lightweight clothing, and never leaving children or pets in parked vehicles (car interior temperatures can exceed 140 degrees F).