The population also includes many older adults and people living with chronic medical conditions. Some residents may live in small apartments with limited ventilation or without effective cooling equipment.
During an extended heat wave, these factors can combine to increase risk.
The French figures in the screenshot therefore illustrate a broader point: extreme heat is not simply a matter of uncomfortable outdoor temperatures. It can affect hospitals, care facilities, public services, workplaces and entire communities.
But the French example should not be confused with a forecast for the United States. A mortality report from Paris cannot identify which American states will experience heat next Tuesday. Different countries, seasons, weather systems and population conditions require separate assessments.
Why One Heat Wave Can Affect Different Groups Differently
A heat wave does not affect everyone in the same way.
Two people living on the same street may experience very different levels of risk. One may spend most of the day in an air-conditioned home, while the other works outdoors. One may have access to a car and a nearby cooling center, while another may depend on public transportation or have difficulty leaving home.
The same outdoor temperature can therefore create different health consequences.
A person with heart disease may have to work harder to maintain normal circulation in hot conditions. Someone taking medication that affects sweating or fluid balance may be more vulnerable to dehydration. A person who lives alone may not have anyone nearby to notice early signs of heat illness.
These differences explain why public-health authorities emphasize targeted protection rather than simply advising everyone to stay indoors.
4. Who Is Most at Risk When Temperatures Rise?
Extreme heat can affect anyone, but certain groups face a greater risk of heat-related illness.
Older Adults
People aged 65 and above are often more vulnerable because the body's ability to regulate temperature can become less effective with age.
Older adults may not recognize thirst as quickly as younger people. They may also have chronic medical conditions or take medicines that influence sweating, blood pressure or fluid balance.
Some live alone and may have difficulty accessing air conditioning, transportation or medical assistance.
A person who appears quiet or unusually tired during a heat wave may not simply be having an ordinary low-energy day. Heat-related illness can begin with symptoms that are easy to overlook.
Family members and neighbors can help by checking in regularly, ensuring that the person has access to a cool environment and asking whether they are drinking enough fluids.
Infants and Young Children
Young children are also vulnerable because their bodies regulate heat differently from adults. They may not be able to communicate clearly when they feel too hot or thirsty.
Children can become dehydrated more quickly, especially when they are active outdoors.
Parents and caregivers should avoid leaving children in parked vehicles, even for a short period. Temperatures inside a vehicle can rise rapidly, creating a potentially fatal environment.
Children should have access to water, shade and regular breaks from outdoor activity. Sports and other strenuous activities may need to be moved to cooler parts of the day or postponed when conditions become dangerous.
Pregnant People
Pregnancy places additional demands on the body. Heat and dehydration can create extra stress, particularly during prolonged exposure.
Pregnant people should pay attention to heat alerts, avoid strenuous activity during the hottest periods and seek advice from their healthcare professional if they have concerns about hydration, medication or symptoms.
A cool indoor environment and regular opportunities to rest can help reduce unnecessary heat exposure.
People With Heart, Lung or Kidney Conditions
The body must work harder to regulate temperature during extreme heat. For someone with an existing medical condition, this additional strain can make symptoms worse.
People with cardiovascular disease may experience increased stress on the heart. Those with respiratory conditions may find hot weather and poor air quality particularly uncomfortable.
Kidney conditions can also complicate hydration because some people need to follow specific fluid restrictions. They should not automatically increase water intake without considering their medical advice.
Anyone taking medication for heart disease, high blood pressure, kidney disease or another chronic condition should ask a healthcare professional whether hot weather changes any precautions they need to follow.
People Taking Certain Medications
Some medicines can affect the body's ability to manage heat.
Depending on the drug, they may influence sweating, blood pressure, alertness, kidney function or the balance of fluids and electrolytes.
Examples can include certain diuretics, medicines with anticholinergic effects, some psychiatric medications and drugs that affect blood pressure.
This does not mean people should stop taking their prescribed medicines when the weather becomes hot. Doing so without medical guidance may create additional danger.
Instead, people who take regular medication should ask a clinician or pharmacist whether they need any specific heat-related precautions.
Outdoor Workers
Construction workers, agricultural workers, delivery drivers, road crews, landscapers and other outdoor employees may face prolonged exposure to direct sunlight and high temperatures.
Physical activity increases the amount of heat produced by the body. Protective clothing and equipment can make it harder to release that heat.
A worker may also feel pressure to finish a task, meet a deadline or avoid taking breaks. This can create dangerous situations when temperatures and humidity are high.
Employers and workers should plan for heat exposure rather than waiting until someone becomes ill. Work schedules can be adjusted, shaded rest areas provided and access to cool drinking water improved.
People Without Reliable Air Conditioning
Not everyone can cool their home effectively.
Some households cannot afford air conditioning or face high electricity costs. Others live in buildings where windows, ventilation or cooling systems are inadequate.
People experiencing homelessness may have even fewer options for escaping extreme heat.
A heat wave therefore raises questions about housing, public services and access to cooling—not just individual behavior.
Cooling centers, public libraries, community facilities and other air-conditioned spaces can provide important relief when they are open and accessible.
5. The Warning Signs of Heat Exhaustion and Heatstroke
Recognizing heat-related illness early can prevent a dangerous situation from becoming a medical emergency.
Two important conditions are heat exhaustion and heatstroke. They are related, but they are not the same.
Heat Exhaustion: When the Body Is Struggling to Cope
Heat exhaustion can develop after prolonged exposure to high temperatures, particularly when a person is physically active or loses substantial fluid through sweating.
Common warning signs include:
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Heavy sweating.
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Weakness or unusual tiredness.
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Dizziness or feeling faint.
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Headache.
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Nausea or vomiting.
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Muscle cramps.
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Cool, pale or clammy skin.
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A fast or weak pulse.
Someone experiencing these symptoms should stop physical activity and move to a cooler place immediately.