How to Be Safe During a Summer Heat Wave

Find out why higher temperatures can feel very different depending on who you are and where you live.

By Laura López González

Heat waves are becoming hotter, longer, more common and deadlier. With another extreme heat wave on the way, we asked Arianne Teherani, PhD, UC San Francisco professor of medicine and cofounder of UCSF’s Center for Climate, Health and Equity, and Gina Solomon, MD, MPH, clinical professor of occupational, environmental and climate medicine about the dangers of heat and what to do to stay safe.

The Center for Climate, Health and Equity is an education and research hub shaping climate action for health by seeking out solutions to ensure health systems respond to the climate crisis.

What should people do to keep safe during hot days?

  • Drink more water. For older people and young kids, don’t wait until you feel thirsty to drink water. Try to keep your fluid intake up throughout a hot spell.
  • Stay in a cool or air-conditioned place. If you don’t have access to a home air conditioner, try to go to a mall, library or cooling center that does.
  • Wear loose, light-colored clothes.
  • Take frequent baths or showers, if you can, to cool down or use a wet cloth to keep your skin moist.
  • Reduce and restrict your physical activity. If you have to be physically active, do it early in the morning or in the evening when temperatures are cooler.
  • Avoid excessive alcohol because it is a diuretic, which causes your body to lose fluids.
  • Check on friends, family and neighbors that could be at a high risk for a heat-related illness. Remember, infants and pets can also be at high risk for illness during hot days.

What common heat-related illnesses should people watch out for?

Heat cramps, heat exhaustion and heat stroke are all things to watch out for.

As our body sweats to cool off, we lose salt and moisture, which can lead to heat cramps. Heat cramps can be a sign of heat exhaustion alongside feeling weak, dizzy, headaches and nausea.

Eventually, if our body temperature rises too high, we can experience heatstroke.

Heatstroke requires emergency treatment. Heatstroke symptoms include red, hot, dry skin; a racing heartbeat; confusion and slurred speech. If left untreated, it can cause seizures, organ damage, coma or even death.

What are signs you may need medical care?

If someone you know is experiencing confusion, a racing pulse or breathing fast and shallow, seek medical attention. If they have symptoms like headache, nausea, vomiting and dizziness get them to a cool place with water right away. If the symptoms get worse or last longer than an hour seek care.

Read the CDC’s FAQ About Extreme Heat for more information.

Who is most vulnerable?

Everybody can get sick on a hot day if you’re not careful, but it’s important to be mindful and check on people you know who might be more at risk:

  • The elderly
  • Young children, including infants
  • Pregnant people
  • Agricultural and other outdoor workers
  • Unhoused people
  • People with chronic illnesses, including lung, heart and mental health conditions
  • People on some forms of medication
  • People confined to their beds or homes
  • Those unable to care for themselves

Does heat have to be extreme to be dangerous?

No. Heat can become dangerous any time people don’t have the resources or protections they need to cope with hot days or repeated exposure to heat.

For example, 105 degrees Fahrenheit in Las Vegas isn’t unusual. People who live there have adjusted with at-home air conditioning. But even 95 degrees Fahrenheit is very hot in San Francisco? Most homes there don’t have air conditioning and people aren’t acclimated to it.

How does heat make us sick?

When it’s hot outside, our body temperature increases too, which can stress our organs. Our body tries to regulate our core temperature by sweating to cool us down or pumping more blood to our skin and limbs to cool.

Eventually, if our bodies can’t bring our temperature down, that can lead to organ damage. Emerging research suggests heat can also cause changes at a cellular level that can increase your risk of heart attack in the wake of a hot spell and lead to chronic kidney disease – even in young people, who historically haven’t been at risk for it.

Studies also show that air pollution can increase during heat waves, which could worsen some heart and lung conditions.

Scientists are only beginning to understand how heat can affect pregnancy, but some work suggests extreme heat might affect fetal development and possibly increase the risk of premature birth.

Can heat worsen mental health?

Studies show that the climate crisis, which is fueling increased temperatures, leads to climate anxiety or climate distress. One of the largest international studies to date, published in The Lancet, found that 60% of 10,000 young people surveyed in 10 countries said they were very or extremely worried about climate change. More than 45% of these young people said their feelings about the climate crisis negatively impacted their daily lives.

Research has also found that as average temperatures in some places rose, suicide rates increased by a similar proportion.

In 2018, scientists reviewed decades of temperature and suicide data for hundreds of thousands of U.S. counties and Mexican municipalities in the journal, Nature. They found that a roughly one-degree Celsius change in monthly temperatures increased the monthly suicide rate by about 1% to 2%, depending on the country. The exact connection between rising temperatures and increased suicide rates aren’t entirely clear and scientists are continuing to study the topic.

Are less wealthy people and countries disproportionately impacted by extreme heat?

Yes, low-income communities and communities of color in the U.S. are disproportionately affected by extreme heat because they often have less green space and tree cover and more pavement, turning neighborhoods into “heat islands” where paved surfaces absorb and radiate heat, and can substantially increase temperatures. People in those areas may also not be able to afford air conditioning.

Although the U.S. is suffering the impacts of the climate crisis, it’s important to remember that wealthier countries have more resources to mitigate and adapt to its effects. Low and middle-income countries do not, and many have historically not been the biggest emitters of greenhouse gases fueling climate change.