Heat Exhaustion or Heat Stroke? How to Tell, and When to Come In

There is one distinction worth knowing before summer, and it is this:

Heat exhaustion is miserable. Heat stroke is a medical emergency that damages
organs and kills people. They start the same way, and the handover between
them can happen in minutes.

Here is how to tell them apart, and what to do about each.

This is not a rare problem here. The Arizona Department of Health Services
puts it at around 4,298 emergency-room visits a year across the state for
heat-related illness, and more than 4,320 heat deaths in Arizona between 2013
and 2024. ADHS also describes Arizona as one of the hottest places on earth
from May to September, which is the part nobody who lives here needs telling.

We see this every summer. It is one of the most common reasons people walk
through our doors between May and September.

The line between them

	Heat exhaustion	Heat stroke
Skin	Cool, clammy, heavy sweating	Often hot and dry — but can still be sweaty
Mental state	Tired, dizzy, irritable, but making sense	Confused, slurring, agitated, stumbling, or unconscious
Temperature	Raised	Very high
Pulse	Fast, weak	Fast, strong
Also	Cramps, nausea, headache, weakness, shortness of breath, fainting	Nausea, headache, seizures
What to do	Cool down and rehydrate; ER if not improving in 30–60 min	Call 911. Start cooling immediately.

If you remember one thing, make it the mental state. Someone who is
confused, slurring, behaving oddly, or stumbling is not tired — that is the
nervous system failing in heat, and it is heat stroke until proven otherwise.

The old advice that heat stroke means "hot, dry skin" has caused real harm.
Someone who collapses while exercising can be drenched in sweat and still be in
heat stroke. Do not use sweating to rule it out.

Heat stroke: call 911 and start cooling now

Cooling begins where the person is. Do not wait for the ambulance to start.

1. Call 911.
2. Get them out of the sun — indoors, or into shade.
3. Remove excess clothing.
4. Cool aggressively. Cold water over the skin, wet cloths with a fan,
   ice packs to the neck, armpits and groin. If a body of cold water is
   available and safe and someone can hold them, immersion cools fastest.
5. Do not give fluids to drink if they are confused or drowsy — they can
   choke.
6. Stay with them and keep cooling until help arrives.

Minutes matter here in a way they rarely do. How long someone spends above a
dangerous temperature is what determines the damage.

Heat exhaustion: what to do

1. Get into shade or air conditioning
2. Lie down, feet slightly raised
3. Loosen clothing and wet the skin; use a fan if the room is cool enough — see
   the note on fans below
4. Sip water or an electrolyte drink slowly
5. Rest properly — not "five minutes and back to it"

Come in if: there is no improvement within 30 to 60 minutes, vomiting
prevents drinking, cramps are severe, or the person has heart disease, kidney
problems, or takes diuretics or blood-pressure medication. And come in at any
point the mental state changes.

⚠️ A fan stops helping above 90°F, and that is counterintuitive

The CDC's guidance is specific: use a fan only while indoor temperatures are
below 90°F. Above 90°F, a fan can increase body temperature.

That matters more here than almost anywhere. A West Valley house with failed
air conditioning goes well past 90°F within hours — and that is exactly the
moment someone reaches for a fan and assumes they have dealt with the problem.
Wet the skin and get to a cooler building. Do not let a fan stand in for
cooler air.

Arizona specifics that matter

The overnight low matters more than the daytime high. A run of nights that
stay above the mid-eighties gives bodies no chance to recover, and that is when
emergency departments here get busy — not necessarily on the single hottest
afternoon.

Monsoon humidity changes the rules. Sweat is the cooling system, and it
works by evaporating. When humidity climbs in July and August, the same
temperature becomes more dangerous, and people who have coped with dry 110°F
days get caught out.

Pavement, playgrounds and car interiors. Asphalt in the West Valley reaches
temperatures that cause contact burns in seconds, and a closed car heats far
faster than most people believe. Both produce emergency visits every summer,
often in children and often in dogs.

The risk is not evenly spread. Infants and young children, adults over 65,
outdoor workers, anyone with heart, lung or kidney disease, people on certain
medications, and anyone without working air conditioning are all at higher risk
at the same temperature.

Staying out of trouble

• Move outdoor work and exercise to early morning. Evening air feels cooler
  but the ground is still radiating the day's heat back
• Drink before you are thirsty. Thirst lags behind fluid loss, particularly
  in older adults
• Add electrolytes for heavy sweating or long sessions, not just water
• Build up gradually if you are new to Arizona summers or returning after
  time away — acclimatisation is real and takes one to two weeks
• Never leave anyone in a parked car, not for a minute, not with the windows
  cracked
• Check on older neighbours and relatives during a heat wave, especially
  anyone living alone or without reliable cooling
• Have a plan for your medicines. The CDC asks people to make one: many
  medicines cause dehydration or overheating, some have to be kept out of hot
  places, and a heat-driven power cut puts anything refrigerated at risk.
  Do not stop or change a medicine without talking to your doctor
• Find your nearest cooling centre before the air conditioning fails, not
  after. Arizona's state heat hub,
  heat.az.gov, maps cooling centres, respite centres and
  hydration stations giving out free water. Look yours up on a cool day and put
  the address in your phone
• If the power is out and you cannot get online, dial 2-1-1. The CDC names
  it as a way to find a building with air conditioning, and a phone call still
  works when a website does not

Frequently asked

Is heat stroke really an emergency if they seem to be recovering?
Yes. Come in or call 911 regardless. Organ injury can be present in someone who
looks better after cooling, and it needs looking for.

Can I get heat illness indoors?
Yes — every summer, in homes without working air conditioning. It does not
require sunshine, and once the room is above 90°F a fan is not a substitute for
cooler air.

How much water is enough?
There is no single number; it depends on the person, the work and the humidity.
Pale urine and no thirst is a more useful gauge than a target.

What about children at sports practice?
Children heat up faster than adults and are less reliable at recognising it.
Practices should have shade, mandatory fluid breaks, and an adult watching for
the mental-state signs rather than waiting for a complaint.

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If someone is confused, stumbling or unconscious in the heat, call 911. For
heat illness that is not improving, El Mirage ER is open 24 hours a day, 7 days
a week at 12000 N El Mirage Rd — no appointment, no referral, and a
board-certified physician sees every patient. Call (480) 237-4922 if you are
unsure. If someone needs hospital admission afterwards, we treat and stabilise
them here and arrange the transfer.

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Sources

The guidance in this article about when to seek emergency care is drawn
from these public sources. Each one is linked so you can read it yourself.

• MedlinePlus (National Library of Medicine) — Heat Illness — https://medlineplus.gov/heatillness.html
• Centers for Disease Control and Prevention — About Heat and Your Health — https://www.cdc.gov/heat-health/about/index.html
• Arizona Department of Health Services — Heat Safety — https://www.azdhs.gov/preparedness/epidemiology-disease-control/extreme-weather/heat-safety/index.php
• HEAT.AZ.gov — Arizona's Central Heat Resource Hub (State of Arizona) — https://heat.az.gov/

This article is general information, not a diagnosis, and it cannot account
for your history or medications. If you are unsure, call us on (480) 237-4922
or come in. If it might be an emergency, treat it as one and call 911.