The heat dome roasting millions of people across the Pacific Northwest and swaths of Canada, sending temperatures in usually temperate places into record-breaking triple digits, has already claimed hundreds of lives. And those are just the ones we can count so far.
Climate change has increased average temperatures by 2 degrees Fahrenheit over the past century, making heat waves like this one more frequent and intense than at any point in recorded history. As the heat soars, so too does the death toll. A worldwide study published last month in Nature Climate Change found global warming responsible for 37% of heat-related deaths between 1991 and 2018. As temperatures tick ever higher, that figure may well rise.
The following is what happens if you’re one of the following people whom extreme heat kills, according to W. Lawrence Kenney, an expert in human thermoregulation at Penn State University.
First, your brain sends messages to your sweat glands, telling them to increase sweat production. Then, your heart starts beating faster to pump blood to the skin, while blood flow is directed away from your liver, kidneys, and gut. That’s your body attempting to make your skin hotter than the air outside, hoping to create a convection phenomenon that moves heat away from you. Sometimes, that alone is enough to create problems for a weak or aging heart.
If heat stroke occurs, your body might get so hot and divert oxygen-rich blood to the skin that it suffocates those vital internal organs, which become hypoxic. Surviving the organ failure that follows might require an emergency transplant.
If your body fails to cool you down, its internal temperature might climb from an average level of between 97 and 99 degrees Fahrenheit to somewhere closer to 104-105 degrees.
“These are the situations where people die of classical heat stroke,” Kenney said during a phone interview Thursday.
At that temperature, the tissues in the brain become affected. You may feel it start as a dull headache. Before long, you might not know where you are or what time it is. You might collapse. You may lose consciousness. Your brain might hemorrhage or begin to swell.
While you struggle to stay awake and avoid dizzying confusion, the excessive internal heat is taking a toll on your gut. The gastrointestinal barrier that keeps bacteria out of your bloodstream, a fence of proteins known as a tight junction, opens the microbial floodgates, unleashing endotoxins into the blood. Your body will likely trigger an inflammatory response. Left untreated, what follows is a cascade of organ failure that leads to all but sure death.
And that’s just part of what we know about how extreme heat kills you.
“It’s important for people to understand that there’s still a lot we don’t know about heatstroke and who’s most susceptible to it,” Kenney said. “That’s because we can’t ethically study it in humans in the laboratory. Much of what we know comes from studies on animal models, like mice and rats, or postmortem examinations of people who have died of heatstroke.”
Heat can kill anyone. But it’s most likely to kill you if you’re older than 65 or have heart problems.
Add to that being poor ― a person renting an apartment in a rundown complex with no air conditioning, the sort of place the local news calls “unlivable” ― and heat might kill you and your neighbor in a single day.
