The Health Risks of our Sweltering Summers

Today is National Heatstroke Prevention Day, and the health threats of climate change are on full display this summer as communities around the world deal with record-breaking heat. Carbon pollution driving climate change is causing significant human suffering by making extremely hot days more common, and increasing the frequency and severity of drought and dangerous wildfires. So how do we keep ourselves safe as the mercury climbs?

Extreme Heat Harms Health in Many Ways

Heat isn’t just an inconvenience, it can kill people in many ways. Every year, extreme heat and humidity kills an average of 1,300 people in the United States, a figure projected to increase significantly in the coming decades as our world heats up. Heatstroke from exposure to extremely high temperatures can be deadly, and extreme heat also causes illness and premature deaths among people with heart, lung, and kidney ailments.

Sweating is the body’s normal way to cool down, but during heat waves, that might not be enough. In that case, the body's temperature rises faster than it can cool down, which can cause damage to the brain and other vital organs:

  • Heatstroke is by far the most serious condition of extreme heat exposure. Be on the lookout for a high body temperature, dry skin (no sweating), a rapid and strong pulse, throbbing headache, dizziness, nausea, or confusion and unconsciousness. If you observe these symptoms in someone, get into the shade as soon as possible, sponge the victim with cool water, and call 911 immediately for medical help.
  • Heat exhaustion is somewhat less severe than heatstroke, and it can be recognized by heavy sweating, paleness, weakness, dizziness, tiredness, fainting and nausea.
  • Heat cramps are a type of muscle pain or spasm, with heavy sweating during exercise.
  • Sunburn is something most of us recognize, but sunburnt skin can’t cool the body as efficiently as it should.
  • Heat rash looks like tiny pimples or small clusters of blisters, and victims should seek cooler, drier places for the rash to clear up.

Beyond the direct physiological risks posed by extreme heat, exposure to high temperatures has important effects on our mental health. For example, people coping with mental illness can be particularly sensitive to the physical effects of heat exposure, such as heat exhaustion and heatstroke. Those who use certain medications like anti-depressants are particularly vulnerable to the effects of extreme heat, and high temperatures themselves can exacerbate existing mental health conditions.

Reducing Risks from Extreme Heat

It’s important to remember that heat deaths and illnesses are preventable—if we take the threat of heat seriously. The simplest advice for handling extreme heat comes from the Centers for Disease Control and Prevention (CDC): “Stay Cool, Stay Hydrated, Stay Informed.”

National Weather Service

Some specific recommended actions to take to deal with extreme heat:

  • To keep cool, wear lightweight, light-colored clothing, use air conditioning when you can, seek out shade, and pace your outdoor activities to avoid the warmest parts of the day.
  • Wear sunscreen, hats, and sunglasses.
  • Don’t leave kids or pets in cars — even with windows cracked open.
  • Eat lightly and avoid hot, heavy meals that add heat to your body. Drink plenty of non-sugary, non-alcoholic fluids that can help replace salt and minerals.
  • Stay informed: ask your medical professional about risks from your medicines, and how extreme heat affects your physical well-being.
  • Stay in touch with weather news and local temperature forecasts – it should tell you about cooling center locations and hours.
  • Knock on the doors of elderly neighbors or people with mobility, health, hearing, or language barriers, to make sure that these community members are safe.
  • If you live in a city, be aware that the urban heat island effect could translate into higher temperatures compared to surrounding areas with less concrete and more green space.
  • For anyone working outdoors in extreme heat conditions, take rest breaks when possible, stay hydrated, and be on the lookout for the symptoms of heat exhaustion and heatstroke.

Addressing the Root Cause of More Extreme Heat

We know that climate-changing pollution is fueling longer, more frequent, and more intense heat waves in the United States and globally. Across 50 large U.S. cities over the last 50 years, observed average heat wave frequency, length, and intensity has increased significantly. The length of the heat wave season has also increased by 6 days per decade, on average. According to the U.S. Third National Climate Assessment, by 2100, historical once-in-20-year extreme heat days could occur every two or three years over most of the US. Check out our interactive map to get a better sense of how the number how extreme heat days has changed over time where you live.

If we keep polluting like usual, extreme heat could make some parts of the world practically uninhabitable. And we can’t just rely on air conditioning to get out of this mess, because new research shows that air conditioning worsens harmful air pollution and contributes to climate change.

Thankfully, we’re not stuck with this worst-case version of the future. By moving decisively toward cleaner, healthier energy sources, we can minimize increases in heat wave severity and frequency—and keep ourselves safer from the many health impacts of heat.

About the Authors

Vijay Limaye

Science Fellow, Science Center

Kim Knowlton

Senior Scientist and Deputy Director, Science Center
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