Experts Reveal The Ways Hot Weather Impacts The Body

Every summer, the news is filled with stories of record-breaking temperatures, suggesting that each year is growing hotter than the last. And that’s bad news for anyone who may be vulnerable to the heat. Scorching weather can affect more than just the elderly and the infirm, too. Even healthy people may be at risk when the mercury rises.

Of course, we know that people tend to sweat a lot in hot weather, and we’re used to quenching our thirst more often during the summer months. But how much do we really understand about how our bodies react to a heatwave? Well, as it turns out, all manner of strange things start to happen beneath the surface once temperatures soar.

It’s been claimed that, in 2019 alone, more than 350,000 people died from conditions relating to extreme heat. And with temperatures set to rise across the planet, we can expect to see these numbers grow even higher. But deadly heatwaves aren’t exactly a modern phenomenon. Warm weather has been causing fatalities across the globe for hundreds of years.

Way back in 1776, for example, the folks in Philadelphia experienced a heatwave that lasted for much of June and July. Today, the city reaches an average high of 86 °F in summer, but most buildings are equipped with air conditioning to keep workers and residents cool. In the 18th century, that wasn’t an option.

Instead, people were forced to endure temperatures into the 90s without so much as an electric fan to stave off the heat. Across the city, historians tell us, doors and windows were flung wide — even though pests threatened to swarm inside. Philadelphians also chose to dress in more lightweight fabrics such as linens, forgoing the heavy wigs that were the fashion at the time.

Despite these precautions, several people lost their lives before the stifling heat finally eased off. Yet that death rate paled in comparison to a tragedy that occurred 120 years later — and also on the east coast of the United States. This time, the epicenter of the heatwave was New York City, where thousands lived in cramped tenement conditions.

In the city’s more overpopulated neighborhoods, the effects of the ten-day heatwave were amplified. And though officials — including Theodore Roosevelt — stepped in to assist those struggling communities, it’s thought that around 1,500 people died as a result of the sweltering conditions. Five years later, high temperatures struck the region once more, resulting in an estimated 9,500 deaths.

Then, in 1936, another fierce heatwave descended on North America, devastating a country already struggling against severe dust storms and the Great Depression. That July, temperature records were smashed from Texas to Minnesota, with one thermometer in North Dakota reading a staggering 121 °F. By the time the heat finally subsided, thousands were dead and crops across the country were left decimated. 

Fast-forward to the modern day, and deadly heatwaves are a relatively common occurrence. In 2010, for example, Russians suffered through temperatures of over 100 °F throughout the months of July and August. In a nation ill-prepared for such extreme conditions, the result was chaos, wildfires, and death, with upwards of 55,000 casualties.

But the most deadly heatwave of all came in 2003, when Europe experienced its warmest summer in more than 450 years. In places, daytime temperatures reached 104° F, while even nightfall brought little relief. And as the weather finally cooled, the catastrophe was revealed to have claimed around 70,000 lives. It also caused billions of dollars worth of damage to crops and infrastructure.

So, why do the heatwaves of the 21st century seem more extreme than their historical counterparts? And why are the death tolls constantly on the rise? Well, according to experts, the average temperature on Earth has risen by approximately 1 °F in the last 100 years. And while that might not seem like much, it’s enough to knock our fragile ecosystem seriously off-kilter.

Climate change isn’t the only thing contributing to an increase in heatwaves around the world. Currently, around 15 billion trees are felled every year — which is bad news if they are not replaced. In fact, recent research suggests that wooded green spaces have a huge role to play in keeping the Earth cool and preventing our cities from overheating.

In a study published in November 2021, researchers analyzed data from 293 different European cities. And they discovered that the spaces with plenty of trees generally had far lower land surface temperatures than the unforested parts. In fact, in central Europe, the difference between the two temperatures was sometimes as much as 53 °F.

“The cooling effect of trees comes largely from shading and transpiration, which is when water within the tree is released as water vapor through their leaves,” The New Scientist’s Chen Ly explained in 2021. “This process takes heat energy from the surrounding environment for evaporation, lowering the surrounding temperature.” The fewer trees there are, then, the less this can happen.

Interestingly, the study also found that green spaces without trees, such as open parks, had little impact on land surface temperature. In some cases, they even appeared to be hotter than more built-up areas nearby. In other words, the loss of forestry in cities could be contributing to global heatwaves — even in places where there’s some provision for nature.

And while scientists consider ways to cool the planet down, the heatwaves just keep coming — and the death tolls continue to rise. So, what exactly is it that’s so lethal about very hot temperatures? Well, there’s no straight answer to that question. There are actually multiple factors increasing fatalities during periods of exceptionally warm weather. 

As you may already know, certain groups are much more at risk during heatwaves than others. Elderly people and infants, for example, can be more vulnerable to the damaging effects of high temperatures than teenagers and adults. Similarly, those with pre-existing health conditions tend to be hit harder than those without. But that’s certainly not all.

According to experts, people with mental health conditions are also more likely to suffer during a heatwave — though nobody is quite sure why. It has been thought that certain medications may play a part in this, although it could also be that this demographic may simply struggle to take care of themselves properly in the heat.

Of course, air conditioning units also play a vital part in keeping people cool and healthy during periods of exceptionally warm weather. In fact, research has shown that access to this technology is the most important factor in preventing heatwave-related deaths. But while the devices are common in many American homes, they are a rarity in many parts of the world.

In Europe, for example, only around 5 percent of homes are equipped with air conditioning — although these statistics are very likely to change as the world grows warmer. Even so, humans can only do so much to adapt their environments in line with these increasingly hostile temperatures. And, eventually, the heat will get to us all.

Typically, the temperature of the human body sits at around 98.6 °F. And if it drops too far, it usually means trouble. In cold weather, biological processes such as shivering help us to keep warm, staving off damaging — and potentially deadly — conditions, including hypothermia. But what happens when things get just too hot?

Well, the good news is that our bodies are pretty good at keeping us cool. When the brain detects rising temperatures, you see, it instructs the blood vessels to dilate, bringing more blood towards the skin’s surface. As a result, we begin losing more heat than before — which is an effective way of keeping our core temperature down.

Unfortunately, this process only works if the body is warmer than the air outside. And in heatwaves, the reverse is often true. But all is not lost, as this is where the sweat glands come in. To cool itself down, the body begins perspiring, creating a layer of liquid that promptly evaporates from the top layer of the skin.

Because the process of evaporation requires heat energy to take place, sweating helps to bring our body temperature back down. But it doesn’t always work. When someone is exposed to extreme temperatures for an extended period, they may stop perspiring altogether. Yes, no sweat at all. And if that happens, they could soon overheat to dangerous levels.

Extreme heat doesn’t just affect the outside of the body, either. The human brain also struggles to function properly in exceptionally warm weather. Apparently, extreme heat can damage the semipermeable membrane known as the blood-brain barrier, and this can allow ions and proteins to build up in areas where they shouldn’t be — with potentially disastrous results.

As a result of this process, the brain can become inflamed, leading to mental confusion. That could explain why some studies have shown a reduction in cognitive capacity during spells of warm weather. And there’s plenty of anecdotal evidence, too. After all, who hasn’t felt cranky and irritable when they’re hot and can’t cool down?

According to the Guardian, a study has also linked hot temperatures with increased suicides and mental health-related hospital admissions. Schizophrenic episodes, it seems, are more common in the heat, as are issues surrounding dementia and depression. And while the warm weather wreaks havoc with cognitive abilities, it’s busy causing chaos elsewhere as well.

The lungs, for example, often struggle to cope because of the stifling conditions high temperatures create. Typically, the air during a heatwave remains still for extended periods, creating an atmosphere thick with pollutants and allergens. This makes it increasingly difficult to get the oxygen we need. But that’s not the only thing that can make it difficult to breathe.

In sunny weather, the emissions created by cars and factories in urban areas can interact with sunlight in a dangerous way, creating what’s known as ground-level ozone, or smog. And when this substance is breathed in, it can damage the lungs and exacerbate existing conditions such as asthma. As temperatures rise, this type of pollution could kill tens of thousands around the world.

But that’s not all. The same processes that cool our bodies down also lower blood pressure, you see, and that comes with its own set of complications. At first, if you overheat, you may find yourself suffering from nausea or dizziness. If you can’t lower your body temperature, however, a whole host of additional symptoms can set in. And often, the heart is among the most vulnerable organs.

When hot temperatures strike, the brain instructs the heart to pump more blood around the body in an effort to cool down. But when a person is already struggling with low blood pressure, this process can be a big challenge for the organ. And if it’s too overworked, the consequences could very well be fatal.

According to one study, conducted from 2008 to 2017 in the United States, excess heat is responsible for as many as 700 heart-related fatalities every year. And, unfortunately, the future looks bleak. The University of Pennsylvania’s Dr. Sameed Ahmed Khatana said in a press release, “The health impacts of climate change have been happening for a while and are likely to continue to get worse with rising temperatures.”

Even the body’s biggest organ, the skin, is vulnerable during heatwaves. Of course, we’ve all experienced the inconvenience of sunburn after spending the day at the beach. But if you regularly expose yourself to too many UV rays, you’re likely to affect the DNA in your skin cells — and any mutation can ultimately lead to cancer.

Worryingly, heatwaves don’t just target specific organs. They can cause an array of additional health problems as well. Excessive sweating can drain the body of vital fluids, causing severe dehydration. At the same time, water loss depletes the supply of electrolytes that we need to remain healthy and fit. That means keeping hydrated is important.

Fatigue is also a big concern during heatwaves, as it only takes a rise in body temperature of a few degrees before things start to go wrong. To compensate, our brains tell our bodies to put the brakes on, and that ultimately may lead to a condition that’s known as heat exhaustion. That explains why we can get so tired during hot weather.

Although you may have heard the terms “heat exhaustion” and “heat stroke” used interchangeably, they actually refer to two very different conditions. The first, fortunately, is fairly mild and can usually be treated without any medical intervention. Even so, sufferers may feel sick and experience vertigo and palpitations. It’s certainly not a pleasant experience.

Typically, heat exhaustion can be dealt with at home by cooling the patient and giving them lots of water to drink. But if they haven’t begun to feel better after half an hour, they could be at risk of heat stroke — a serious condition that requires instant medical attention. In this case, body temperature rises to 104 °F, and this may in turn lead to hallucinations.

If you’re suffering from heat stroke, things can get serious quickly. Without the proper treatment, you may lose consciousness or experience seizures — an outcome that can ultimately prove fatal. So, it’s important that you take your health seriously during periods of hot weather — and that you know when you need to seek professional help.

It’s a lesson we all could do well to take on board. Heatwaves are set to become more common as our climate changes, with temperatures across the planet expected to rise by 5° F by the middle of the 21st century. And with humidity levels also predicted to increase, spending a day in the sunshine may soon become a lethal occupation.