Heat exhaustion means heavy sweating, cool clammy skin, weakness, and nausea — move to air conditioning, lie down, and sip cool fluids. Heat stroke means a body temperature above 103°F with confusion and often hot, dry skin because sweating has stopped — that is a 911 call. Heat stroke damages the brain, kidneys, and heart within minutes, and the person experiencing it is usually too confused to recognise it.
If you remember one thing: confusion is the dividing line. Someone who is miserable but lucid has heat exhaustion. Someone who is not making sense has heat stroke until proven otherwise.
Side by side
| Heat exhaustion | Heat stroke | |
|---|---|---|
| Body temperature | Raised, usually under 103°F | Above 103°F (39.4°C) |
| Skin | Cool, pale, clammy, heavy sweating | Often hot and dry — but can still be sweaty in exertional cases |
| Mental state | Tired, irritable, but making sense | Confused, agitated, slurred speech, or unconscious |
| Pulse | Fast and weak | Fast and strong |
| Other signs | Muscle cramps, headache, nausea, dizziness, fainting | Vomiting, seizure, loss of consciousness |
| What to do | Cool actively; if no better in 30 minutes, come in | Call 911 and start cooling immediately |
Two cautions about that table. First, exertional heat stroke — in a hiker, athlete, or outdoor worker — often presents with the person still sweating heavily, so wet skin does not rule it out. Second, heat exhaustion can progress to heat stroke quickly, so “it’s only heat exhaustion” is a reason to act, not to relax.
What to do for heat stroke
While someone calls 911:
- Move them into air conditioning or deep shade.
- Remove excess clothing.
- Cool aggressively. Cold water immersion is the most effective method if you can manage it — a bath, a pool, even a stock tank. Otherwise: soak them with cool water, fan them continuously, and put ice packs at the neck, armpits, and groin where large blood vessels run close to the surface.
- Do not give fluids to anyone confused or unconscious — they can choke.
- Keep cooling until help arrives. Minutes of cooling now matter more than anything that happens later.
Do not wait to “see if they perk up.” Cooling in the first half hour is what determines the outcome.
What to do for heat exhaustion
Get out of the heat, lie down, elevate the legs, loosen clothing, and apply cool wet cloths or a cool shower. Sip cool water or an electrolyte drink — steadily, not in gulps.
Come to our Emergency Room if there is no clear improvement within 30 minutes, if vomiting stops fluids staying down, if the person has heart disease or takes diuretics or blood pressure medication, or if muscle pain is severe and urine turns dark brown or cola-coloured. That last one can mean rhabdomyolysis — muscle breaking down and overwhelming the kidneys — which needs intravenous fluids and monitoring.
Heat cramps are the early warning
Painful spasms in the legs, arms, or abdomen during or after exertion in heat are your body flagging fluid and salt loss. Stop, get cool, drink something with electrolytes, and gently stretch. Do not go back out for the rest of the day. Cramps that continue beyond an hour, or in anyone with heart disease, deserve a visit.
Exercising in Arizona heat
You can train here safely, but not by pretending the climate is negotiable.
Timing beats toughness. Before 7am or after 7pm in summer. The hours from 10am to 4pm are not a challenge to be overcome; the asphalt and rock radiate heat long after the air temperature peaks, so a 6pm trail can be hotter than the forecast suggests.
Acclimatise over 10 to 14 days. Your body genuinely adapts — sweating earlier and conserving salt — but it takes about two weeks of gradual exposure. Newcomers and returning seasonal residents are at the highest risk precisely because they feel fine at first.
Pre-hydrate, then drink on a schedule rather than by thirst. Add electrolytes for anything over an hour.
Know your medications. Diuretics, beta blockers, antihistamines, some antidepressants and antipsychotics, and stimulants all impair your ability to shed heat or sense thirst. If you take any of them, talk to us at the Medical Clinic about what that means for summer activity.
Watch the humidity, not just the temperature. During monsoon, higher humidity means sweat evaporates less and cooling fails faster — a 105°F monsoon afternoon is more dangerous than a 110°F dry one.
Stop at the first symptom. Dizziness, nausea, headache, cramping, or a sudden chill in the heat all mean stop now.
Who is most at risk here
Infants and young children, adults over 65, people with heart or lung disease, people with diabetes, outdoor workers, athletes, anyone taking the medications above, people without reliable air conditioning, and anyone new to the desert. Alcohol raises risk considerably, which matters for pool days and holiday weekends.
Never leave a child, an adult, or a pet in a parked car. Interior temperatures can rise dozens of degrees in a matter of minutes, and cracking a window does not prevent it.
And check on neighbours during heat events — particularly older residents living alone. An air conditioner that fails in July is a medical emergency waiting to happen, and a knock on the door is sometimes the whole intervention.
Where to go
Call 911 for confusion, a temperature above 103°F, seizure, collapse, or hot dry skin in the heat — and start cooling while you wait.
Come to our Emergency Room — 9700 N. Saguaro Blvd, open 24 hours, no appointment — for heat exhaustion that is not improving, persistent vomiting, dark urine after exertion, or if you are simply not sure. We can give intravenous fluids, check kidney function and electrolytes on site, and cool you properly. ER: (602) 671-7990.
Book our Medical Clinic to review medications before summer, or if you repeatedly struggle in the heat: (602) 671-7981.
Related reading: signs of dehydration in children and adults and desert hiking safety.
Sources
- CDC — Heat-related illnesses: signs and first aid
- National Weather Service — Heat safety
- Arizona Department of Health Services — Extreme heat
- Mayo Clinic — Heat stroke