Heat domes are bad news for your body

"The problem with a heat dome is that your body just doesn't have a chance to catch up," Dr. Allison Edwards says.

During a heat dome, it’s hot not just during the day but also at night, extending the duration and intensity of hot temperatures. Plus, there’s a lot of humidity, meaning things don’t evaporate quickly — including sweat.

Edwards is a family physician and medical advisor to Sesame. She breaks down the science behind what heat domes do to your body, why it can become life-threatening and how to keep yourself safe.

Stage 1: Your body adapts

"The first thing that heat does to your body is that your heart rate goes up a little bit. The blood vessels in your skin actually expand and get bigger,” Edwards explains.

This expansion allows your body to reroute your blood to your skin and let the heat dissipate through its surface, rather than hold it near the core of your body where your organs are.

(MORE: What is a heat dome? Explaining the deadly weather pattern behind America's most dangerous summer days)

Sweat is one of the main mechanisms that the body uses to cool down, so that’s one of the first things it will try to do too.

"Your body can do this for hours to try and regulate temperature," Edwards said. "Too long for one person might be eight hours, too long for another person might be two or three hours in the exact same conditions." 

Stage 2: Your body starts to struggle

After a few hours, you might actually start to become dehydrated, and you’ll experience a lack of electrolytes if you start losing more water than you're replacing.

Edwards said this is when your body can start to shut down blood flow to some of the organs to make an extra effort to get that blood flowing toward the skin.

"If you're really, really hot and all of a sudden you stop sweating, that could be a sign of impending heat stroke,” Edwards said.

Pause: How to respond now

The first step is always to take a break, go inside, find some air conditioning and cool down, she advises. 

If you don’t have access to going inside a building, even a car with a working air conditioner is better than nothing. Sitting in the shade is definitely less effective, especially if you’re experiencing strong symptoms, but it’s definitely cooler than direct sunlight.

You know your body is in good shape when you’ve gone somewhere to cool down and spent enough time there to stop sweating.

(MORE: This is the best thermostat setting for summer)

“We've all had the phenomenon where we've been outside on a hot day, we go inside, we take a shower, we get out of the shower, and we are still sweating,” she said. “That means your body temperature is still high."

The next best thing, if you’re still unable to cool your body, is to immerse yourself in water, she said.

Stage 3: Heat stroke — a medical emergency

Heat stroke is a life-threatening condition. Untreated heat stroke results in death in up to 80% of cases, Edwards says.

The biggest sign of it, according to Edwards, is confusion — if you're unable to concentrate to a degree that's not normal for you.

If you experience this, you should first get out of the heat as fast as you can, and second, possibly even call for medical help or head to the emergency room.

Organs may begin to shut down. The heart and the lungs are preserved until the very end, but if things get bad enough, they will shut down too.

"The body is pretty impressive at adapting to heat,” Edwards said. "You just gotta listen to those signs that your body is giving you."

Content writer Ada Wood enjoys exploring the stories that science and climate teach us about our natural world and how it influences the way we live in it.