By Heather Brown

EDITOR’S NOTE: This was first published in July of 2020.

MINNEAPOLIS (WCCO) — We know it’s been toasty this summer. According to the MN State Climatology Office, last month was in the top-10 for hottest Junes in Minnesota.

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July already appears to be headed that way. On Wednesday, the heat index went above 100.

“I was more than exhausted,” said one delivery biker in downtown Minneapolis. “I had a stomach ache, I was fatigued.”

So, why does the heat make us feel crummy? Good Question.

“It’s your body’s way of telling you that your body temperature is rising out of control,” says Dr. Enoch Arhinful, a general internal medicine physician with Allina Health.

Human bodies regulate core temperatures in a number of ways. The body needs to keep within a narrow window of temperature, whether it’s warm or cold outside.

Dr. Arhinful says one way is thermoregulation, where the nerve endings in the body send a signal to the “thermostat” in the brain.  The brain then tells the heated-up body to send more blood flow to the skin.

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“That is a way of dissipating the heat in the blood through our sweat pores,” he says.

But, with more blood going to the skin, less blood goes to major organs like the gut, the brain and the heart. That can cause stomach aches, headaches and exhaustion.

The fatigue stems from the body working hard.

“A lot of it has to do with your heart rate going up,” says Dr. Arhinful. “It takes a lot of energy for your heart to keep pace with that rate and it tires the heart out.”

Humidity makes it even harder for the body to regulate its temperature. When a person sweats, the moisture evaporates from the skin to pull heat away.

In high humidity, it’s harder for the sweat to evaporate and cool the body down.

“Once you take away that protective mechanism for regulating temperature, you run into a situation where body temperature will start to rise rather rapidly,” says Dr. Arhinful.

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So, he recommends drinking water, not over-exerting and keeping cool inside on hot and humid days.

Heather Brown