Everyone can see what heat can do to the outside of your body, but not everyone knows the threat heat imposes on what you can't see.
"There's a system whereby the heat begins to actually internally cook the person, so you begin to get muscle damage," says Dr. George Fredrick, Director of the Family Medicine Residency Training program at Phoebe Northwest.
This happens when your core temperature reaches 104 degrees. And when muscles get damaged, they release harmful materials in the blood, which can cause serious problems like kidney failure.
"The blood flow itself begins to be limited and when it occurs, it begins to affect the brain," says Dr. Fredrick.
Causing hallucinations and confusion. In addition to the brain, heat can also cause seizures.
"When the sodium gets very low, then the brain usually goes into what we call a seizure activity, it begins to fire sporadically," says Dr. Fredrick.
Firemen have to deal with the heat year round and the way their protective gear works is it's designed to keep out the heat while they're battling the flames, but in doing so, it keeps a lot of the heat in, which makes dehydration a main concern.
"We push our guys to extreme limits of heat exhaustion, even to the point at times where we have to turn them over to EMS to let them cool down, give them oxygen, rehydrate them with IV's," says Battalion Chief, Keith Ambrose.
"Give them a break periodically and automatically, whether they say they need it or not," says Training Officer Jason Ribolla.
Which is also a good idea for anyone spending an extended length of time outdoors. Doctors recommend eating and drinking lots of water or sports drinks with electrolytes, stay away from sodas and alcohol. These can cause you to be even more dehydrated.