The first sign of heat exhaustion is feeling thirsty and it can quickly turn more serious from there.
Dr. Brian Sorensen, a trauma doctor at Hendrick Medical Center, also said certain medications you take --- like blood pressure pills, antihistamines, antipsychotics or antidepressants -- can worsen symptoms of heat exhaustion.
In hundred degree temperatures, the only thing many people want to do is stay inside a cool, air-conditioned room. But for those who make their living working outside, staying in the shade is not an option.
"You just never get used to it," laughed a construction worker originally from Tennessee, but working in Texas for the season.
We're not even a week into summer and the heat is officially on.
Mauricio Garcia has been doing construction and bricking work for 14 years and said the scorching sun never lets up.
"It's construction, you can't just be inside the building all day, you have to stay in the heat," Garcia said.
But when you make your living working outdoors, you have to find ways to cope.
Some tips shared by workers on a site in North Abilene: keep a wet towel over your head, stay in the shade, take plenty of breaks, and of course, stay hydrated.
"I don't want to get sick," said one worker. "I've heard of that happening to people and they just never recover from it."
Just last week, Richard Flores, an Abilene gardener, suffered heat exhaustion.
He said he felt dizzy, realized he wasn't drinking any water, and had to take a longer-than-usual break.
Despite the 100-degree temperatures, there is a reason everyone's still out there.
"It's my job, how I make my living," Garcia said. "I can't complain."