Anyone who has spent a summer in Phoenix or Tucson has heard the warnings: Stay indoors when temperatures soar. Still, every year people in those cities fall victim to heat-related illness and even death.
Dr. Sam Keim, professor and chair of the UA Department of Emergency Medicine and director of the Arizona Emergency Medicine Research Center, estimates that one or two people a day visit Banner – University Medical Center Tucson with heat-related illness 
in the summer months. The most serious is heat stroke, which can cause permanent disability and is fatal about 50 percent of the time, he said.
"Even in the best emergency departments and ICUs in the world, your chances of survival are only 50/50 once you reach this dangerous stage," said Keim, also a professor of in the UA's Mel and Enid Zuckerman College of Public Health.
Heat stroke is a medical emergency that occurs when the body is unable to control its own temperature through its regular adaptive systems, such as perspiration. It often is accompanied by confusion or seizures and a body temperature of 104 degrees or higher.
In southern Arizona, those at greatest risk of death from heat-related illness include undocumented immigrants attempting to cross the Arizona-Mexico border and out-of-town visitors who may not be familiar with the dangers of desert summers, Keim said.
At least five people died last month while hiking in record heat in Tucson and Phoenix.
The Centers for Disease Control and Prevention identifies these warning signs of heat-related illness:
Heat Stroke: This is the most serious form of heat-related illness. Medical attention should be sought immediately.
- An extremely high body temperature (above 103 degrees)
- Red, hot and dry skin, with no sweating
- Rapid, strong pulse
- Throbbing headache
- Dizziness
- Nausea
- Confusion
- Unconsciousness
Heat Exhaustion: a milder form of heat-related illness that can develop after several days of exposure to high temperatures and inadequate or unbalanced replacement of fluids.
- Heavy sweating
- Paleness
- Muscle cramps
- Tiredness
- Weakness
- Dizziness
- Headache
- Nausea or vomiting
- Fainting
Keim offered these tips for preventing potentially deadly heat-related illness:
- First and foremost, try to stay indoors when temperatures reach 100 degrees or hotter. Outdoors should be considered a "dangerous environment," Keim said. It should be noted, however, that people can experience heat-related illness at lower temperatures if the exposure is prolonged or the person is dehydrated.
- If you must go outdoors, or your occupation requires you to work outside, be sure to have an "exit strategy,"Keim said. Make certain you have access to either shade or an air-conditioned building and that you have a way to call for help if necessary.
- Hydrate, hydrate, hydrate. If you must be outdoors, Keim said, you should be drinking at least 20 ounces of water an hour. And don't wait until you are thirsty to drink. Also, avoid alcohol. It will only dehydrate you more and decrease your normal decision-making capabilities.
- Don't think you're in the clear because you are otherwise healthy. There is a common misconception that only the very young or very old are at risk for heat-related illness, Keim said. While these populations may be most vulnerable, anyone can fall victim. Statistics suggest that the median age of undocumented border crossers who die in the desert is 34 — "in the prime of their lives," Keim said. So all people of all ages should take precautions.
More information about extreme heat and heat-related illness is available on the CDC website.