Extreme Heat Poses Rising Threat to Heart Health, American Heart Association Warns

The American Heart Association is sounding the alarm on the dangers of extreme heat, which it calls the leading weather-related cause of death in the United States, according to the National Weather Service. As temperatures climb across the country, the organization emphasizes that heat can put serious strain on the heart, leading to life-threatening complications, particularly for those with cardiovascular disease.

Research published in the American Heart Association's journal Circulation projects that heat-related cardiovascular deaths could more than double in the coming decades. A report in the Journal of the American Medical Association found that more than 2,300 people died from heat exposure in the U.S. in 2023 alone.

“Heat forces the heart to work harder,” said Manesh R. Patel, M.D., FAHA, volunteer president of the American Heart Association and chief of the division of cardiology at Duke Health. “When your body is trying to cool down, your heart rate increases and your blood vessels expand. For people with heart disease, and even those who are otherwise healthy, that added strain can become dangerous quickly.”

The body's natural cooling mechanism—sweating—leads to fluid loss and dehydration, while the heart must pump more blood to regulate temperature. Together, these changes significantly stress the cardiovascular system.

The American Heart Association recommends several steps to protect yourself in extreme heat. Avoid outdoor activity between noon and 3 p.m., when temperatures are highest. Wear lightweight, light-colored clothing, a hat, and sunglasses, and use sunscreen. Stay hydrated by drinking water before, during, and after time outdoors, and avoid alcohol and caffeinated drinks that contribute to dehydration. Take breaks in the shade or a cool indoor space.

Knowing the warning signs of heat-related illness can save lives. Symptoms of heat exhaustion include headache, cool pale clammy skin, fast but weak pulse, dizziness or fainting, weakness or muscle cramps, and nausea or vomiting. If these occur, slow down physical activity, move to a cooler place, cool down with cold water, and rehydrate. Medical attention may be needed. Heat stroke is a medical emergency—call 9-1-1 immediately if you or someone else experiences a body temperature above 103°F, hot red dry or damp skin, rapid strong pulse, confusion, headache, loss of consciousness, or nausea.

Physical activity remains essential for heart health, even in summer. The AHA suggests shifting exercise to early morning or evening hours, or moving workouts indoors to air-conditioned spaces like gyms or community centers. Activities such as walking, swimming, biking, skating, or even gardening provide cardiovascular benefits.

For more information on staying heart-healthy in the heat, visit heart.org. Additional resources are available from the American Heart Association, including tips on staying active in hot weather and hydration infographics.