PHOENIX (3TV/CBS 5) - "Like, in the winter time, I can run up, but when it's hot I have to stop take a breath, drink water to stay hydrated and keep going," said Yesenia Vidales, hiker.
The temperatures may be in triple-digit territory, but that isn't stopping people from hiking in the middle of the day.
"For me, it's like 105 and below, and I'm good to go, but anything hotter than that is just too hot," said hiker Chris Mckown.
But the heat has already put several hikers in danger.
"It's very important to be aware of your body because it can come on very quickly," said Dr. Leah Hillier with Banner Health.
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That "it" Hillier is referring to is heat exhaustion and heat stroke. And there is a broad spectrum of symptoms.
"We see simple things like muscle cramping or just feeling tired or fatigue," said Dr. Hillier.
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More severe symptoms include dizziness, confusion, nausea, vomiting or passing out.
"Worst case scenario we actually see seizures and even death," said Dr. Hillier.
"If you get too tired, turn around. The heat is no joke," said McKown.
There are ways to protect yourself.
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"The most important and critical thing for heat is water," said Dr. Hillier.
"I try to bring a big jug like this," said Vidales.
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How much water depends on the person and temperature. Dr. Hillier recommends people drink 20 ounces before they go outside and then drinking up to 30 ounces per hour they are out in the heat.
"I bring two bottles of water full bottles. I use one and then the other is just for emergency in case I need it or someone else needs it," said McKown.