How extreme heat affects your body (and how to protect yourself)

O Human Body does not survive high temperatures unscathed. Extreme heat can cause everything from discomfort to serious illnesses, such as dehydration, heat exhaustion, thermal shock, heatstroke, dysfunction of vital organs and even death.

With this in mind, we have created a complete guide that will explain how heat affects your body and what measures you should take to protect yourself on hot days. See below:

Temperature records in Brazil

In recent months, the National Institute of Meteorology (INMET) conducted a detailed analysis of the country's climate, using average air temperature data collected at meteorological stations distributed throughout Brazil. The conclusion of the survey shows that temperatures this year were above the historical average during the months of July to October.

When analyzing data from the last 60 years, the National Institute of Space Research (INPE) concluded that there has been a significant increase in the number of days with heat waves, which is more than double in the last two decades. The study, commissioned by Ministry of Science, Technology and Innovation, revealed trends in rainfall patterns, maximum temperatures and other extreme weather indices.

Using information from more than a thousand meteorological stations for maximum temperature series, and more than 11.000 rain gauges for precipitation data, the researchers carried out segmented analyzes for three distinct periods: 1991-2000, 2001-2010 and 2011-2020.

During 1991-2000, the maximum temperature had a increase of approximately 1,5°C. However, between 2011 and 2020, this increase reached 3°C in some areas, especially in the Northeast and nearby regions. The average maximum temperature in this area of ​​the country, during the reference period, was 30,7°C. This value gradually increased to 31,2°C in 1991-2000, 31,6°C in 2001-2010, and reached 32,2°C in 2011-2020. Each year, the temperature tends to rise more.

Among the hottest places in Brazil, the highest temperatures recorded in the last heat wave were:

• Araçuaí (MG) – 44,8°C
• São Romão (MG) – 43,4°C
• Porto Murtinho (MS) – 43,4°C
• Corumbá (MS) – 43,4°C
• Rio de Janeiro (RJ) – 42,5°C
• Cuiabá (MT) – 42,0°C
• Boa Vista (RR) – 40,6°C
• Valparaíso (SP) – 40,2°C

In the main capitals of the Southeast, the most populous region, the situation had considerable repercussions. Since Sunday (12), an intense heat wave has remained over Brazil, increasing drastically in the states of São Paulo and Rio de Janeiro, mainly. Only on Monday (13), the meteorological station in Santana Lookout, in the north of the capital of São Paulo, registered 37,7°C, a heat rarely seen in the place.

On Tuesday (14), Rio de Janeiro reached a new heat record, with a thermal sensation of 58,5°C recorded in the neighborhood of Guaratiba, in the west of the city. The actual temperature was 35,5°C, even in the same region. On Saturday (18), early in the morning, the city had a thermal sensation that exceeded 59ºC, according to data from the Rio Alert System from the city hall.

For those curious, the reason behind all this weather, with increases of up to 5°C in temperatures, results from a convergence of factors: a blockage of atmospheric pressure, the phenomenon El Niño and climate change. Furthermore, the expansion of the high atmospheric pressure zone can also be highlighted, spanning from northern Argentina to the southern Amazon. This configuration prevents cold fronts from entering these areas, which contributes to the maintenance and intensification of this heat in several regions of Brazil.

What is the ideal external temperature for the body?

It can be a little fascinating and, at the same time, very delicate how the human body reacts to extreme temperatures. Our body is sensitive to more exorbitant variations, especially when it comes to excessive heat. Intense cold can also wreak havoc by slowing metabolism, but it is not as immediately lethal as heat. So, what should the external temperature be for the human body to remain in balance?

According to a survey by University of Roehampton, presented at the 100th anniversary conference of Society for Experimental Biology (SEB)Apparently, humans can tolerate 40°C to 50°C when they are not active. The conclusion was based on the resting metabolic rate (RMR), which shows the amount of energy an organism consumes while at rest. Furthermore, it has been found that it can increase when people are exposed to hot and humid conditions.

Much work has been done on the range of temperatures in which different species of animals prefer to live in terms of minimum metabolic rates and therefore low energy expenditure. But, strangely, we have little data when considering the upper limits of our thermal neutral zone.

Lewis Halsey, researcher and professor at the University of Roehampton

In one study, participants were exposed to a temperature of 28ºC, along with an air humidity of 50%, which would be conditions considered ideal for maintaining the stability of body temperature and human metabolism. When the temperature rose to 40ºC, with humidity reduced to 25%, the individuals' metabolic rates increased by an average of 35%, but their body temperatures did not follow this increase. When reaching 50ºC, with 50% humidity, the average body temperature increased by around one degree. In this scenario, the metabolic rate increased by 56% and the heart rate by 64%. The conclusion was that in these extreme conditions, even sweat was not effective in cooling the body.

Variations in these effects in individuals with different characteristics, such as age and physical fitness, were also investigated. According to the Professor Halsey, some differences were notable in the heart's response to heat in different groups, one of the most surprising being between the sexes. It seems that men and women have very different cardiovascular system reactions to heat.

In short, as far as we know, the ideal average external temperature to keep the body in balance is around 28ºC, but stops functioning in a healthy way when thermometers exceed 40ºC. Still, according to research that corroborates findings previously mentioned in the book Life on the Limit – The Science of Survivala by British physiologist Frances Ashcroft, it is also possible to withstand temperatures of up to 127 °C for up to 20 minutes.

How heat affects your body

The human body has the ability to regulate its temperature naturally to protect itself, keeping it relatively stable, thanks to the regulatory nerve center in the hypothalamus. However, high temperatures can destabilize this balance and affect our health. Although we have already mentioned measures, it is still important to remember what exactly happens when the body overheats.

According to American Medical Association, when we exceed 37,8°C internally, it is considered fever or hyperthermia, accompanied by symptoms such as chills, intense sweating and malaise. If the temperature reaches 39°C, it can trigger mental confusion and delirium. At 42 ºC, proteins begin to unfold and the functioning of cells is compromised, causing the body to collapse. From here, convulsions may occur, indicating the urgent need for medical assistance. Therefore, it is good to always pay attention to the signs.

Sweat is our main response, the only way we can deal with the heat. The liquid lost through sweat needs to be replaced by drinking more water. If we fail to do this, we can become dehydrated, a condition that can result in dizziness and feeling faint, what we call “heat exhaustion.”

Julie Davies, Professor at UCL Global Business School for Health

At a certain point, the body can no longer sweat enough to keep itself cool. If the body temperature significantly exceeds 35 to 37 degrees, there is a risk of heart attack or heatstroke. To a large extent, this can affect the heart, since this situation is related to low oxygen levels, and consequently, if there is not enough oxygen for the brain, it can be extremely dangerous.

Recent research in New York also revealed that heat can intensify mental health problems. On hot days, there has been an increase in emergency room visits from patients with anxiety, schizophrenia, dementia and substance abuse.

How to protect yourself from the heat

The lack of adequate infrastructure to deal with heat waves in Brazil is a constant challenge. However, there are individual measures that people can take to face this extreme heat scenario.

Although the Brazilian population resorts to beaches and swimming pools on high temperature days, it is important to highlight that, according to World Health Organization (WHO), it is still crucial to avoid the sun and seek shade to protect yourself from the heat in extreme cases. Furthermore, it is necessary to avoid leaving children or animals in parked cars and prioritize spending a few hours in cool places to maintain balance. Outdoor physical exercise should only be carried out during cooler times of the day and, above all, maintain constant hydration.

Nowadays, we already have air conditioning. However, with the extreme temperatures in Brazil and the constant use of devices by the entire population, it is common to face unforeseen events such as a lack of electricity. In these cases, according to Wendell Porter, professor of agricultural and biological engineering at University of Florida, here are some tips for staying safe during hot days:

• Hydration: Drinking water is the first step, since when the body is experiencing heat and needs to cool down, this will only be possible with sufficient moisture.

• Cold bath: According to the professor, body temperature can decrease with cold water. No wonder, this is exactly one of the solutions when you have a fever.

• Use of cold cloths: A great way to cool down is to place a cold cloth or ice packs on your wrists or around your neck. These are points that have blood vessels close to the skin, and therefore allow the body to cool more quickly.

• Close curtains and blinds: A suggestion for homes with windows facing the sun is to close the curtains or blinds during the morning and afternoon. This helps prevent direct entry of it, preventing excessive heating inside. Additionally, installing blackout curtains can insulate the room and reduce temperature increases throughout the day.

• Breathable sheet: Cotton sheets or blankets are recommended to keep you feeling cool at night, as cotton is one of the most “breathable” materials. The lower the thread count of cotton, the more breathable it is. This is because lower thread count means less weave per square inch.

• Sleep in lower places: If the heat is preventing you from sleeping at night, consider sleeping in another location if possible. Since heat tends to build up, choose a cooler room and set up a temporary sleeping area.

• Do not refrigerate blankets and clothing: According to Porter, it is not advisable to follow the common suggestion of chilling or freezing wet socks, blankets and clothes and using them while sleeping. This recommendation is due to the amount of heat that items can absorb from your body during the night, and then heat up too quickly. This would only result in damp fabrics, which is not desirable.

• Close doors: If a room without vents or registers is not being used, consider leaving the door to that space closed to restrict cold air to only occupied areas of the home.

• Use of kitchen/bathroom extractor fan: Remember to turn on the extractor fan in your kitchen to remove hot air that builds up after cooking, or in the bathroom to eliminate steam after showering.

• Energy efficient lamps: Incandescent bulbs generate more heat than LED bulbs. To make the switch, it is suggested to gradually replace the light bulbs at home with the most energy-efficient ones.

• Cooking in the morning: The heat from the oven can disperse throughout the house, so the tip is to try to keep the heat concentrated in one area. Another option is to cook outdoors on a grill to prevent heat from spreading inside the house, as will the choice of the first time of the day. The sooner you do what you need to do with the use of heat, the cooler the rest of the day will be.

• Frozen foods and treats: Eating ice cream can offer momentary relief from the heat. But it's also important not to overindulge in sugar when you feel overheated or at risk of overheating. As pointed out by Porter, what few know is that sugar can increase metabolism and cause an internal feeling of heat.

Does the air circulator work?

The air circulator, despite appearing similar to a common fan, has the capacity to cool larger spaces and is recommended especially for those who suffer from allergies or respiratory problems. They are ideal for distributing air throughout the room evenly, while fans are more effective at directing airflow to specific areas. But the question is: is it worth it?

With its operation based on an electric motor and angled steel blades, the circulator operates differently from a traditional fan. With an aerodynamic system, it not only pushes the air forward, but also attracts it to the center and distributes it throughout the environment — which helps to reduce the concentration of particles in the air and favors those people with allergies. In conclusion, its name ends up being self-explanatory.

Furthermore, the circulator is also known for its much quieter operation, which makes it a great option for those who value a peaceful environment to rest.

Here, we have separated some of the best options on the market in the store. showmetech No. Magalu:

• Air Circulator with 3 speeds – Wincy (R $ 315,84)
• Premium Air Circulator – Mondial (R $ 195,22)
• C50 Oscillation Air Circulator – Britânia (R$ 371,07)
• Portable Turbo Air Circulator – Wincy (R$ 411,21)
• Fix Powerful Air Circulator – Deccore Ja (R$ 252,19)

Recommended air conditioners

Choosing the ideal air conditioner can transform the experience of thermal comfort at home, especially when it is a place with extreme heat temperatures. Among models from renowned brands such as LG, Samsung and others, there is a variety of options, from portable systems to efficient split.

We have selected seven models that stand out for their quality, efficiency and functionality to meet different individual needs and preferences.

Split Samsung Digital Inverter Ultra

O Samsung Digital Inverter Ultra offers a rapid cooling experience, up to 43% faster, and is highly efficient, providing energy savings of up to 73% due to its technology Inverter. With a 10-year warranty on the compressor, it features an antibacterial filter that not only removes up to 99% of bacteria and allergens but also keeps the air clean and fresh.

Furthermore, its intelligent operation avoids frequent “on-off” in order to guarantee an always comfortable environment, as well as the good sleep which stands out for creating an ideal climate for a peaceful night's sleep. With an advanced system, the model is capable of cooling spaces quickly, reaching a pleasant temperature 43% faster than conventional ones.

The air conditioner also includes an automatic cleaning function that operates after shutdown, removing dust and moisture from the heat exchanger, which prevents the growth of bacteria and mold.

the air conditioning Samsung Digital Inverter Ultra is available at our partner store:

• Samsung Digital Inverter Ultra – Cold: 9.000 BTU/h (R $ 2.469,05)
• Samsung Digital Inverter Ultra – Cold: 12.000 BTU/h (R$ 2.788,20)
• Samsung Digital Inverter Ultra – Hot and cold: 12.000 BTU/h (R $ 4.666,01)
• Samsung Digital Inverter Ultra – Cold: 18.000 BTU/h (R $ 4.849,00)
• Samsung Digital Inverter Ultra – Hot and cold: 22.000 BTU/h (R $ 5.218,20)

Split Samsung WindFree Connect

O Samsung Wind Free Connect stands out for an innovative system that cools the environment without the use of direct air currents. With more than 23.000 micro air vents, it offers a comfortable environment, simulating external conditions.

Owning the technology digital inverter ultra, it is up to 77% more economical compared to conventional models, in addition to reaching the desired temperature 43% faster. Its filtration system is very effective and also eliminates up to 99,9% of microorganisms, with a remotely controlled internal cleaning mode and an automatic self-cleaning system.

The air conditioning stands out for supporting voice commands and allowing control through the brand's exclusive application, the SmartThings. With it, it is also possible to monitor energy expenditure in real time.

the air conditioning Samsung Wind Free Connect is available at our partner store:

• Samsung Wind Free Connect – Cold: 9.000 BTU/h (R $ 2.877,55)
• Samsung Wind Free Connect – Hot and cold: 9.000 BTU/h (R$ 2.974,41)
• Samsung Wind Free Connect – Cold: 12.000 BTU/h (R $ 2.603,07)
• Samsung Wind Free Connect – Hot and cold: 12.000 BTU/h (R $ 3.537,89)

LG DUAL Inverter Voice

Advances in air conditioning technology offer smart solutions for maintaining cleaner, healthier indoor environments. The technology UVnano with ultraviolet LED lamps, present in models from leading brands, eliminates up to 99,99% of impurities, including viruses, bacteria and mold, from inside the device, which ensures that the air released is pure and safe at all times.

With Dual Inverter compressor, the desired temperature is reached up to 40% faster and maintained stably, while significantly reducing energy consumption by up to 70% compared to conventional models.

With LG DUAL Inverter Voice, concern for comfort is also taken into account: the high-precision ventilation system makes operation quieter, operating from just 19 decibels, the equivalent of a quieter environment than a library. Furthermore, offering additional safety, the device withstands voltage spikes in the electrical network.

the air conditioning LG DUAL Inverter Voice is available at our partner store:

• LG DUAL Inverter Voice – Cold: 9.000 BTU/h (R$ 2.338,20)

LG DUAL Inverter Voice Artcool

O LG DUAL Inverter Voice Artcool seeks to always provide a very clean environment. Just like all the brand's models, which focus on eliminating impurities, their lamps UVnano Ultraviolet LEDs provide the purest air throughout the space without the need for replacement.

Also equipped with the Dual Inverter compressor, it reaches the ideal temperature very quickly, in addition to saving electrical energy, thanks to the reduction in compressor starts.

with the function Self Cleaning, air conditioning prevents the formation of bacteria and mold, keeping the inside of the device clean. Furthermore, to make them easier to find, the buttons are illuminated even in low-light environments.

the air conditioning LG DUAL Inverter Voice Artcool is available at our partner store:

• LG DUAL Inverter Voice Artcool – Hot and cold: 18.000 BTU/h (R $ 5.599,00)
• LG DUAL Inverter Voice Artcool – Hot and cold: 22.000 BTU/h (R $ 5.746,55)
• LG DUAL Inverter Voice Artcool – Hot and cold: 24.000 BTU/h (R $ 6.849,00)

LG DUAL Portable Voice Inverter

With ease of installation and incredible practicality, the LG DUAL Portable Voice Inverter stands out, for the most part, for its silence, reaching just 44 decibels thanks to the exclusive engine and the famous Dual Inverter compressor, which eliminates unnecessary noise and also allows for precise cooling.

The model has three operating modes: Refrigerate, Ventilate e Dehumidify, which help to adjust the environment according to the weather conditions, whether to cool down on hot days, circulate the air or reduce humidity on rainy and humid days.

With an installation kit including hose and mounting plate, it simplifies the process and even saves space. The wheels allow you to easily move it around the space, while the mounting plate adapts to different windows, both horizontally and vertically.

What's more, with the app LG ThinQ, it is also possible to control and monitor the air conditioning from wherever you are. Integration with the Google Assistant it also allows control by voice commands.

the air conditioning LG DUAL Portable Voice Inverter is available:

• LG DUAL Portable Voice Inverter – Cold: 14.000 BTU/h (R$5.099,00)

Elgin Eco Cube Portable

Here, practicality and ease of installation are essential characteristics of the portable air conditioning concept, allowing consumers to carry out the installation without having to hire accredited installers.

O Eco Cube Elgin Portable Air combines a modern and clean design to suit different environments. Temperature regulation can also be easily controlled via the device's digital panel or via the included remote control, and efficient air distribution is guaranteed by adjusting the fins.

The model also offers a specific mode for removing humidity from the environment, which can be activated when necessary. With side handles and swivel wheels, transport becomes practical and convenient for use in different spaces.

the air conditioning Elgin Eco Cube Portable is available at our partner store:

• Elgin Eco Cube Portable – Cold: 9.000 BTU/h (R$ 2.309,00)

Philco Virus Protect Portable

O Philco Virus Protect Portable prioritizes a healthier environment and eliminates up to 99% of fungi, mites, viruses and bacteria. With four distinct functions, it is versatile for any space, some of which include the Sleep function, oscillation for better cooling and the Ionizer for cleaner air. Furthermore, the remote control provides quick adjustments and allows you to manage the device without leaving the comfort of your sofa.

The antibacterial filter, which is easy to remove and clean, ensures superior filtration to maintain air quality and prevent diseases, even using a less harmful ecological gas. It not only ensures safety but also reduces the impact on the ozone layer.

the air conditioning Philco Virus Protect Portable is available at our partner store:

• Philco Virus Protect Portable – Cold: 12.000 BTU/h (R $ 3.283,41)
• Philco Virus Protect Portable – Hot and cold: 12.000 BTU/h (R $ 3.432,99)

See also: Brazil is preparing for the biggest heat wave in history, with temperatures above 45°C

Sources: Euronews, CNN, Folha de S. Paul, EurekAlert, Estadão, G1

reviewed by Glaucon Vital em 14 / 11 / 23.