Hypothermia Indoors When the Heat Fails

Before the cold snap

One warm room beats a warm house

Heating 2,400 square feet without utility power is not realistic. Heating 150 square feet is. Plan the room before the storm, not during it.

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Hypothermia indoors kills more quietly than hypothermia outdoors, because nobody expects it. There is no blizzard to respect, no obvious moment of danger — just a house that got to 48°F on the third day of an outage and an older relative in a recliner who seemed a bit vague at dinner. Hypothermia is defined as a core body temperature below 95°F, against a normal of about 98.6°F, and a still, unheated house reaches people slowly enough that they never notice it happening.

Why an Indoor Case Sneaks Up

A body at rest generates roughly 100 watts of heat. When the furnace stops, the house begins shedding more than that through walls, glass and floors, and the occupants make up the difference out of their own core temperature. It takes hours or days rather than minutes, which is precisely the problem: gradual cooling produces no dramatic signal, and the first thing to go is the judgment you would need to recognize it.

Three things speed it up indoors. Damp clothing, including sweat from hauling firewood, strips heat many times faster than dry cloth. Sitting still for hours in a chair drops heat production to its floor. And alcohol, which feels warming because it dilates skin vessels, actually dumps core heat faster while blunting the shivering response.

The Stages, and What You Would Actually See

Stage	Core temp (approx.)	What you see
Mild	90–95°F	Hard shivering, clumsy hands, slurred or mumbled speech
Moderate	82–90°F	Shivering fades, confusion, memory loss, drowsiness
Severe	Below 82°F	Shivering stopped, weak pulse, shallow breathing, unresponsive

The CDC’s list of adult warning signs is worth memorizing as a set, because they rarely arrive one at a time: shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech and drowsiness. In babies the picture is different — bright red, cold skin and very low energy, often with no shivering at all, because infants have limited ability to shiver.

The most dangerous transition is the one that looks like improvement. When shivering stops, people assume the person has warmed up. Shivering stopping while the person is still cold and getting vaguer means the body has run out of the fuel to do it. That is a deterioration, not a recovery.

Who Goes Down First

Older adults. Blunted temperature regulation, less muscle mass, often less able to feel that a room is cold. Many indoor hypothermia deaths are people over 65 in their own homes.
Infants and small children. High surface area for their mass, and a baby sleeping in a cold room cannot do anything about it.
Anyone who has been drinking. Alcohol accelerates heat loss and removes the warning signals.
People with hypothyroidism, diabetes, stroke history, spinal cord injury, or dementia, and those taking sedatives, antidepressants or antipsychotics — several of these blunt thermoregulation directly.
Thin, immobile or exhausted people, including anyone who has spent the day working outdoors in the storm.

If any of these describe someone in the house, they get checked on by name every couple of hours during a cold outage. Not “is everyone okay” shouted down a hallway — go look at them, and ask a question that requires a real answer.

What to Do

Safety — call 911 now if: the person is confused, unusually drowsy or hard to rouse; their speech is slurred; they have stopped shivering while still cold; they are breathing slowly or shallowly; their pulse is weak or irregular; or they are an infant with cold, bright red skin and very low energy. Hypothermia at this stage needs medical treatment, not blankets. While you wait for help, handle the person gently — rough or jarring movement can trigger a dangerous heart rhythm in a badly chilled body. Nothing on this page is a substitute for emergency care or for your doctor’s advice.

For a person who is cold, shivering, alert and talking normally, and while you wait for help in any worse case:

Move them to the warmest room in the house, out of any draft, and off a cold floor onto a chair or mattress.
Get wet clothing off and replace it with dry layers. Wet cotton against skin is worse than nothing.
Warm the core first — chest, neck, groin, armpits — with dry blankets or sleeping bags, plus a hat. Warming the arms and legs first can push cold blood back to the heart.
A warm, sweet, non-alcoholic drink helps only if the person is fully alert and able to swallow safely. Never give fluids to someone confused, drowsy or unresponsive.
Skin-to-skin contact under blankets is a legitimate field method and works indoors too.

What not to do: no rubbing or massaging the limbs, no alcohol, no hot bath or shower, and no space heater aimed directly at bare skin. Rapid surface warming of a significantly chilled person can drop blood pressure and destabilize the heart. Slow, dry, core-first warming is the goal.

Keeping the House Above the Line

Prevention here is unglamorous and effective. Pick one interior room, ideally small, with few exterior walls and no large windows, and concede the rest of the house. Close it off, hang a blanket over the doorway, and put everyone’s sleeping arrangements in it. Bodies plus a few candles’ worth of incidental heat hold a small room far above what a whole floor will do.

Sleeping bags rated below freezing beat any quantity of household blankets, and a foam pad or air mattress between a person and the floor matters more than the covers on top. Dress in layers with a hat indoors; a startling share of heat leaves through an uncovered head and neck when you are sitting still.

If you are using a fuel-burning heater to hold that room, you have traded one hazard for another. Anything burning propane, kerosene or wood in an enclosed space needs ventilation and a working alarm, and the symptoms of carbon monoxide poisoning overlap uncomfortably with the confusion and drowsiness of hypothermia.

The Part Worth Remembering

If you retain one thing from this page, make it the pairing: confusion plus cold is an emergency, and a person who stops shivering is getting worse, not better. Everything else — the sleeping bags, the closed-off room, the thermometer in the hallway — exists so that nobody in the house ever reaches the point where those two signs matter.

Frequently Asked Questions

How cold does a house have to get for hypothermia?

There is no single number, because exposure time, clothing, dampness, age and health all change the answer. Cases occur in houses in the 50s and 60s Fahrenheit when a vulnerable person sits still in them for a day or more. Treat a house below about 60°F as a situation to manage rather than tolerate.

Can you get hypothermia while asleep in bed?

Yes, and it is one of the more common indoor patterns, particularly in older adults and infants. Heat production is at its lowest during sleep and nobody is there to notice the early signs.

Is a hot shower a good way to warm someone up?

Not for anyone who is more than mildly chilled. Fast surface rewarming can cause a blood pressure drop and cardiac problems. Dry blankets and core warming are safer, and moderate-to-severe cases belong in an ambulance.

Should I check someone’s temperature with a regular thermometer?

Most household thermometers do not read reliably below about 94°F, so a “normal” reading on a cold person means little. Judge by how the person looks and behaves, and call 911 based on that rather than a number.