Hypothermia begins when your core body temperature drops below 95°F (35°C), and the earliest signs are easy to miss or dismiss as just “being cold.” Shivering, clumsiness, and unusual sleepiness are the first red flags. Recognizing these symptoms early matters because hypothermia can progress quickly, and by the time it becomes severe, the person affected may no longer realize anything is wrong.
Early Signs of Mild Hypothermia
Mild hypothermia covers a core temperature range of 90°F to 95°F (32°C to 35°C). At this stage, your body is aggressively trying to warm itself. The hallmark signs include intense shivering, chattering teeth, exhaustion, slow or clumsy movements, and growing sleepiness. Your reaction time slows noticeably, and fine motor tasks like zipping a jacket or tying knots become difficult.
Outdoor safety instructors sometimes teach the “umbles” as a memory aid: stumbles, mumbles, fumbles, and grumbles. If you or someone around you starts tripping, slurring words, dropping things, or becoming unusually irritable in cold conditions, those are warning signs that the body is losing heat faster than it can produce it. Shivering at this stage is actually a protective response. It can boost your metabolic heat production by two to five times the normal resting rate. That’s an enormous amount of energy expenditure, which is why exhaustion sets in so fast.
How Moderate Hypothermia Looks Different
As core temperature falls to between 82°F and 90°F (28°C to 32°C), something counterintuitive happens: shivering may slow down or become less intense, even though the person is colder. Mental confusion deepens. Speech becomes difficult to understand. The person may stop complaining about the cold altogether, which bystanders sometimes misread as improvement. It is the opposite.
Coordination deteriorates further. Walking in a straight line becomes nearly impossible. Decision-making breaks down in ways the person themselves cannot recognize. This is what makes moderate hypothermia so dangerous. The very organ you need to identify the problem and take action, your brain, is the one being impaired. People at this stage often resist help, insist they’re fine, or make irrational choices like sitting down in the snow instead of continuing to move toward shelter.
Severe Hypothermia: When Shivering Stops
Below 82°F (28°C), the body loses its ability to shiver entirely. The cold has overwhelmed the mechanism that generates heat, and without external warming, the person cannot recover on their own. Breathing becomes very slow and shallow. The pulse may be faint or difficult to detect. The person may appear unconscious or barely responsive.
Two bizarre behaviors sometimes appear in severe hypothermia. One is “paradoxical undressing,” where the person removes their clothing despite freezing temperatures, likely because damaged blood vessel nerves create a sudden false sensation of burning heat. The other is “terminal burrowing,” where the person crawls into a small, enclosed space like a closet or under a bed. Both behaviors are signs of a medical emergency. At core temperatures below 75°F (24°C), the condition is classified as “profound” hypothermia, and survival depends entirely on advanced hospital care.
How to Check Without a Thermometer
Most people won’t have a way to measure core temperature outside a hospital. Standard oral or forehead thermometers often can’t read low enough to register hypothermia. So in practice, you’re relying on behavioral and physical cues.
Start with shivering. If someone is shivering hard but still thinking clearly and moving with reasonable coordination, they’re cold but likely not yet hypothermic. If shivering is paired with confusion, clumsiness, or slurred speech, assume mild to moderate hypothermia and act. If shivering has stopped but the person feels ice-cold to the touch and is barely responsive, assume severe hypothermia.
Touch the skin on the person’s torso, not just their hands. Cold hands are normal in chilly weather. A cold chest or abdomen suggests the core is losing heat. Also pay attention to skin color. In babies, hypothermia often shows up as bright red, cold skin combined with unusually low energy, a pattern that’s distinct from the pale or blue-tinged skin more common in adults.
What to Do When You Spot the Signs
The first priority is stopping further heat loss. Get the person out of the cold environment if at all possible. Remove wet clothing, which pulls heat from the body far faster than dry air does. Then insulate them. Layer dry blankets, sleeping bags, or even spare clothing around the person, and place a barrier between them and the ground, since cold ground conducts heat away rapidly.
For active rewarming, apply heat to the chest and armpits using hot water bottles, warm (not hot) packs, or similar heat sources wrapped in cloth to prevent burns. Small hand warmers are not effective for raising core temperature. They simply don’t produce enough heat. Warm, sweet drinks can help someone with mild hypothermia who is alert enough to swallow safely, but never give alcohol, which dilates blood vessels near the skin and actually accelerates heat loss from the core.
One critical warning: do not put a hypothermic person in a hot shower or warm bath. The sudden warming of the skin causes blood vessels at the surface to open wide, which can drop blood pressure sharply and lead to cardiovascular collapse. Rewarming needs to happen gradually and from the core outward.
Handling a Severely Hypothermic Person
If someone has moderate or severe hypothermia, handle them as gently as possible. A cold heart is electrically unstable, and rough movement or jostling can trigger a dangerous heart rhythm. Keep the person lying down and avoid unnecessary repositioning.
If you can’t detect a pulse, check for a full 60 seconds before concluding there isn’t one. A severely hypothermic heart may beat so slowly and faintly that a quick check will miss it. If there truly is no pulse after that full minute, begin chest compressions. But if any pulse is present, even an extremely slow one, do not start compressions. In a cold body, even a minimal heartbeat is circulating some blood, and compressions on a beating heart can cause it to stop.
Anyone with moderate or severe hypothermia needs hospital care. Field rewarming can stabilize someone with mild symptoms well enough that transport isn’t necessary, but below that threshold, professional intervention is required.
Who Is Most Vulnerable
Hypothermia doesn’t require extreme cold or wilderness conditions. It can happen in temperatures well above freezing, especially when wind, wet clothing, or water immersion are involved. Certain groups are at higher risk. Older adults lose the ability to regulate body temperature efficiently and may not sense cold as acutely. Infants have a high surface-area-to-body-mass ratio, meaning they lose heat disproportionately fast. People who are intoxicated are at particular risk because alcohol impairs both temperature regulation and the judgment needed to seek warmth. Thin or malnourished individuals have less insulating body fat and fewer energy reserves for shivering.
Even indoors, hypothermia can develop in poorly heated homes during winter, especially among elderly people living alone. If you’re checking on someone in a cold home and they seem confused or unusually drowsy, consider hypothermia as a possibility even if they haven’t been outside.