How Extreme Heat Affects Your Health

Summer in South Florida comes with record-breaking heat, and this year will be the same. Approximately one-third of the year in Miami is at or above 90°F (32.2°C) degrees. High humidity increases the number of days with an extreme heat index, which measures how hot it feels when air temperature and relative humidity are combined.

Chronic heat stress that South Floridians experience is not just uncomfortable; it poses significant health concerns. As global temperatures rise, people can experience a range of health issues directly related to chronic heat stress exacerbated. Heat stress affects a range of diseases and disorders, including cardiovascular diseases and dry eyes.

Understanding how extreme heat affects our health is critical to mitigate its health risks.

Naresh Kumar, Ph.D. a public health sciences expert at the University of Miami Health System, and Dushyantha Jayaweera, M.D., FACP, an infectious disease doctor and researcher at the University of Miami Health System, explain how heat stress affects our bodies and how to manage heat-induced health problems effectively.

How heat affects your cardiovascular system and overall health

Most people living in South Florida know to watch for signs of heat stress during episodes of extreme heat. However, exposure to higher temperatures over time changes our bodies more subtly.

“If you are exposed to relatively higher temperatures compared to the past, it affects how your body metabolizes energy,” says Dr. Kumar.

For example, cold temperatures cause goosebumps and shivering, which directly burns energy. When it’s hot, that process is reversed. “We usually think about burning energy through walking, running, or exercising. Exposure to cold temperatures is another way of burning energy. If the temperature is hot, that energy won’t burn, meaning people will begin to gain more weight unless they exercise more to compensate for the lack of cold exposure,” says Dr. Kumar.

Hotter temperatures also facilitate a sedentary lifestyle by forcing people to stay inside, which can inhibit calorie expenditure.

What’s the cardiovascular impact of extreme heat?

Heat stress occurs when the body cannot sufficiently cool down, leading to overheating. This condition triggers sweating and vasodilation, where blood vessels dilate to increase blood flow to the skin, facilitating cooling through sweat evaporation.

However, this process places additional strain on the heart, which must pump more blood to manage the increased flow.

Constant exposure to heat over time can cause an increase in heart rate. During exposure to high temperatures, the cardiovascular system is under immense pressure. The heart has to work much harder to pump blood to deliver nutrients and oxygen and simultaneously cool the body.

Those who work outdoors and sweat constantly draw water from their blood for sweat production, which may cause dehydration and decreased blood volume availability to vital organs. This, in conjunction with vasodilation, where the veins under the skin expand, increases the workload of the heart and can exacerbate existing heart conditions or lead to new cardiovascular issues.

“Your entire cardiovascular system is fired up during that heat stress. You can’t just treat the symptoms like changes in heart rate without addressing its underlying cause,” says Dr. Kumar.

Tips to stay safe in high temperatures

1. Take intermittent breaks in cooler environments when spending long periods of time outdoors.
2. Wear lightweight, light-colored clothing outdoors.
3. Stay hydrated to significantly reduce the strain on your cardiovascular system.
4. Cautiously exercise, but keep moving. Hot days can make us more sedentary. Find ways to safely keep moving indoors or exercise in the early morning or late evening when temperatures are cooler.

How extreme heat affects the air and our health

Higher temperatures and humidity increase bio-aerosols, which are airborne particles that originate from biological sources. These include pollen, fungi and bacteria. Higher temperatures keep bioaerosols airborne for longer in both indoor and outdoor environments.

Mold, common in South Florida, can trigger asthma and allergies and exacerbate other inflammatory diseases. Homes in Miami can develop mold caused by the contrast between hot and humid outdoor air and cool indoor air. When hot and humid air enters indoors, the excess moisture condenses indoors, which facilitates mold growth in air vents and under carpets. “Outdoors, you have pollen, and indoors, you have mold. These conditions are likely to intensify with higher temperatures, which are likely to exacerbate allergies and immunological disorders,” says Dr. Kumar.

As South Florida has more hot days and humidity, fungi also change. Dr. Jayaweera recently had a patient diagnosed with histoplasmosis, an infection caused by breathing in spores of a fungus often found in bird and bat droppings normally in states like Arizona and Indiana. “We don’t see this much here, but he got histoplasmosis in Miami.”

Humid air and allergies also cause dry eyes. A study from Dr. Kumar in Clinical Ophthalmology found that dry eye signs and symptoms vary in the region each month, with the highest severity of symptoms occurring in spring and fall. This corresponds with peak allergy season and weather fluctuations.

Safety tips for managing air quality in high temperatures

1. Dry eyes: Dry eye syndrome can be exacerbated by hot, humid climates and cold, dry climates. In humid regions like South Florida, having a dehumidifier and periodically changing the filter can help reduce dry eyes exacerbated by indoor humidity. Eye drops can provide temporary relief, but it won’t solve the underlying cause of the disease.
2. Stay aware of air quality. Hot weather can exacerbate air pollution, leading to respiratory issues, especially those with asthma or other respiratory conditions. Monitoring air quality and staying indoors or wearing an N-95 mask outdoors during high air pollution levels can help protect your respiratory health.

How extreme heat increases mosquito-borne diseases

Hotter summers in South Florida increase mosquito-borne diseases. These include the Eastern equine encephalitis virus detected in chicken flocks and infectious diseases that are not normally prevalent in the region.

Malaria and dengue fever were once eliminated in the United States, but a few cases have been reported yearly. “We never used to see malaria, but now there are a handful of cases. It doesn’t take too long for mosquitoes to breed and for this to take off,” says Dr. Jayaweera.

Safety tips for managing mosquito-borne illnesses

Bug spray, sealed window screens, and draining stagnant water can all help decrease mosquito bites and breeding in general.

1. Eliminate standing water around your home by regularly draining water from garbage cans, gutters, flowerpots, kiddie pools, and other containers.
2. Use insect repellent and wear protective clothing outdoors, such as long sleeves and pants. Choose repellents with effective ingredients like DEET or picaridin.
3. Repair broken screens on windows and doors.

Protecting your medication from the heat

Some medication needs refrigeration, but even shelf-stable medication can be inactivated in extreme temperatures. This can pose problems when refilling prescriptions, says Dr. Jayaweera. “I’ve had cases where a patient keeps the medicine in the car when the temperature is very high, which makes the medicine ineffective.”

Safety tips for medication management in high temperatures

1. Avoid storing medication in hot spaces: High temperatures can degrade even shelf-stable medications. Store medications in a cool, dry place away from direct sunlight. Avoid leaving them in cars, which become extremely hot in South Florida –– even during a quick errand.
2. Check medication storage instructions: Always read the label or consult your pharmacist to ensure you store your medications correctly. If you’re unsure about the stability of your medications in the heat, ask your pharmacist for advice.
3. Use insulated containers: If you carry your medications, use containers with ice packs to keep them at a stable, cool temperature.

5 recommendations for staying healthy in extreme heat

1. Watch for signs of heat-related illness: Heat-related illnesses like heat exhaustion and heatstroke can be serious. Knowing the early signs, such as excessive sweating, fatigue, nausea and dizziness, can help you take action early and prevent a more severe condition.
2. Eat electrolyte-rich foods: Incorporate foods rich in electrolytes into your diet during hot weather episodes. Bananas, oranges, potatoes, spinach, yogurt and coconut water are good sources of potassium. Salty snacks like pretzels or nuts can help replenish sodium levels when sweating.
3. Protect Your Skin: Besides sunburn, extreme heat can exacerbate conditions like eczema and psoriasis. Using sunscreen and moisturizing regularly can help protect and soothe your skin.
4. Keep cool at night: High temperatures can disrupt sleep, which is important for overall health. Use fans, air conditioning or other cooling methods to ensure a comfortable sleeping environment.
5. Stay informed: Track weather forecasts and heat advisories in your area. The National Weather Service’s new HeatRisk tool indicates how the heat may affect you in your location. Knowing when extreme heat is expected can help you plan activities and take necessary precautions.

South Floridians are used to heat, but stay aware and safe when temperatures are particularly oppressive. To stay healthy in the heat, stay hydrated, wear weather-appropriate clothing, use humidifiers, and take breaks in cooler environments.

Heart health information reviewed and approved by Nikolaos Spilias, M.D., an interventional cadriologist at UHealth.

Wendy Margolin is a contributor to UHealth’s news service.

Tags: Dr. Naresh Kumar, Dr. Nikolaos Spilias, Dushyantha Jayaweera, heat advisory, heat impacts