Hypothermia in Arizona: It Is a Body Temperature, Not a Weather Forecast

If somebody is cold and confused, or cold and cannot be roused, call 911. Warm them gently and slowly. Never with a heater, a hot water bottle, a hair dryer or a hot bath, and do not rub them.

The National Weather Service defines it with a number that has nothing to do with the thermometer outside:

“When your body temperature sinks below 95°F, you have hypothermia, a serious health hazard.”

Ninety-five degrees, measured in a person. And the mechanism, in the Weather Service’s words, is just as indifferent to the forecast: “Hypothermia occurs when the body loses heat faster than it can produce it.”

Which is why this page exists in a state people associate only with heat. Nothing in either of those sentences requires freezing weather. What it requires is losing heat faster than you make it — and wet clothing, wind, exhaustion, alcohol and a long night will do that at temperatures nobody would call cold.

Why a desert night is the setup

This part is our reasoning rather than the Weather Service’s, and it follows from the mechanism above:

The swing is the problem. A pleasant afternoon and a night twenty-five or thirty degrees colder is an ordinary Arizona day, and people dress for the afternoon they walked out into. A hike that runs long, a breakdown on a back road, a fall, a night out longer than planned — and the clothing that was correct at four o’clock is not the clothing you need at nine.

Add water and wind and it accelerates. Rain, a creek crossing, sweat that cooled, or a monsoon-season soaking, and the heat loss the definition describes is no longer theoretical.

And “it is Arizona” is the belief that keeps people out too long. Winter visitors, in particular, arrive with a mental model of this state that has no cold in it at all.

What it looks like, and it is subtler than shivering

The Weather Service’s description of somebody becoming hypothermic: they “feel cold and sluggish, or you are having trouble thinking clearly.”

Trouble thinking clearly. That is the same sign that matters most in heat illness, and for the same reason — it means the problem has reached the organ that would otherwise tell the person to do something about it.

So the person affected is the least reliable judge of it. Somebody who is slow, vague, stumbling or making poor decisions in the cold is not tired. Confusion is the emergency, in either direction of the thermometer.

And frostbite, which has its own signs

The Weather Service names them:

“Redness or pain in any skin area may be the first sign of frostbite.” First sign — so redness and pain are not the mild version, they are the start.

Then: “a white or grayish-yellow skin area, skin that feels unusually firm or waxy, numbness.”

Numbness is on that list, and numbness is comfortable. The affected area stops complaining at exactly the point it needs attention. The areas the Weather Service says are most prone are uncovered skin and the extremities, such as hands and feet.

Warming somebody: gently, centre first, and never with heat

This is the part almost everybody gets wrong, and the Weather Service’s instructions are specific.

Move them somewhere warm and warm the middle of the body first — “Move the victim inside to a heated location and begin warming the center of the body first.”

Do not rub them — “Don’t rub the person or handle them roughly.”

Get wet clothing off — “change into dry clothing immediately if you are wet.”

Warm, emphatically not hot. The Weather Service’s own wording carries the emphasis: “Get in a warm, NOT hot, bath and wrap your face and ears in a moist, warm, NOT hot, towel.”

And this list of things not to use: “Don’t get near a hot stove or heater or use a heating pad, hot water bottle, or a hair dryer.”

Every instinct on that list is the wrong one. The heater, the hot shower, the hot water bottle, rubbing the hands — those are what a helpful person reaches for, and all of them are named as things not to do.

No alcohol, either. Shivering is the body generating heat, and alcohol suppresses it — so a drink to warm somebody up works against the only heat they are still making.

If they are unconscious

The Weather Service says: “If the person is unconscious, administer CPR.”

Call 911 first and let the dispatcher direct you. They will tell you whether and how to begin, and stay on the line while you do it. That is better than anything a web page can teach in advance, and it is the same advice this site gives for any collapse.

Who it happens to

“Most are seniors, according to the National Institute of Aging, but some are children and young adults.”

So it is not primarily a hikers-and-climbers problem. It is disproportionately an older-person problem — including indoors, in a house that is not being heated, which is the version nobody photographs.

Where to go

Call 911 for confusion, drowsiness, unresponsiveness, slurred speech, somebody who cannot stop shivering or who has stopped shivering while still cold, or anybody found outside overnight.

Come to an emergency room for suspected frostbite of any degree, for numb or waxy skin, for somebody who was very cold and is not recovering normally once warm and dry, and for any older adult who has been cold for a long period. Rewarming an injury properly matters more than it sounds, and it is not a job for a bathroom.

Our emergency rooms are open every hour of every day and are walk-in, with a full laboratory in the building. Go to the nearest one, and if another emergency department is closer, that one is the right answer tonight.

If you are unsure, come in — this list is not exhaustive and you are not expected to take somebody’s core temperature yourself.

Questions people actually ask

It was 50 degrees. Can that really cause hypothermia? Hypothermia is defined by a body temperature below 95°F, not by an air temperature. Wet, wind, exhaustion, alcohol and enough hours will get somebody there in weather nobody would call cold.

He has stopped shivering, so he must be warming up? Treat that as a reason to call rather than a reassurance, particularly if he is still cold or is not thinking clearly. Shivering is heat production, and its absence is not obviously good news.

Can I put him in a hot shower? No. The Weather Service says warm, not hot, and names heating pads, hot water bottles, hair dryers and hot stoves as things not to use. Warm the centre of the body, gently.

My fingers went numb hiking and they are fine now. Numbness is on the frostbite list, and “fine now” after rewarming is still worth a mention. If there is any colour change, firmness, waxiness or persisting numbness, be seen.

My elderly mother’s heating is broken and she says she is fine. Seniors are the largest group affected, and “I am fine” is not a measurement — the same problem as checking on somebody in a heat wave, running the other way. Go and feel how cold the house actually is.

We are on a trail and it is getting dark and cold. Call early rather than late, and being found is half the problem — stay put once you have called, and stay as dry and out of the wind as you can.

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Hypothermia is a body temperature below 95°F, not a forecast. Warm somebody gently, from the centre, never with heat — and call 911 for confusion or unresponsiveness. Both of our emergency rooms are open 24 hours a day, every day of the year — walk in, no appointment and no referral. Find your nearest emergency room →

Related reading: when to call 911 on a trail · which door do you need

Sources

40. Cold Weather Safety — National Weather Service, National Oceanic and Atmospheric Administration. https://www.weather.gov/safety/cold
41. During Extreme Cold — National Weather Service, National Oceanic and Atmospheric Administration. https://www.weather.gov/safety/cold-during

This article is general information, not a diagnosis. It does not teach resuscitation — call 911 and follow the dispatcher. If you are unsure, come in — this list is not exhaustive and you are not expected to assess a core temperature yourself. If it might be an emergency, treat it as one and call 911.