The signs of hypothermia start with intense shivering and progress to confusion, slurred speech, and eventually loss of consciousness as the body’s core temperature drops below 35°C (95°F). Recognizing these signs early matters because hypothermia affects the brain, making it harder for the person experiencing it to realize they need help.
Early Signs: What Happens First
The body’s first defense against cold is shivering. Strong, uncontrollable shivering is the most obvious early sign that core temperature is dropping. At this stage, classified as mild hypothermia (core temperature between 32°C and 35°C, or roughly 90–95°F), the body is still actively trying to generate heat through muscle contractions.
Alongside shivering, you’ll notice clumsiness and lack of coordination. Simple tasks like zipping a jacket or handling a phone become difficult. Speech may start to sound mumbled or slightly slurred. The person may seem unusually drowsy or low-energy, and confusion or memory lapses can appear even at this early stage. Cold hands and feet, pale skin, and a puffy or swollen face are also common early indicators.
These mental changes are what make hypothermia particularly dangerous. Because the cold impairs thinking, people often don’t recognize what’s happening to them. If you’re with someone who’s been exposed to cold and they seem confused, clumsy, or unusually tired, don’t wait for more dramatic symptoms to act.
Moderate Hypothermia: The Warning Signs Escalate
As core temperature falls between 28°C and 32°C (roughly 82–90°F), the signs become more alarming. Shivering actually decreases or stops entirely. This is not a sign of improvement. It means the body is running out of energy to generate heat.
At this stage, breathing and heart rate slow noticeably. The skin may take on a bluish color, particularly around the lips and fingertips. Mental function declines further, sometimes producing hallucinations. Muscles become increasingly stiff, and the person’s reflexes weaken. Blood pressure drops, and the heart may begin beating irregularly. Loss of consciousness can occur.
One critical point: jarring or rough movements at this stage can trigger dangerous irregular heartbeats. If you’re helping someone with moderate hypothermia, handle them gently.
Severe Hypothermia: A Life-Threatening Emergency
Below 28°C (about 82°F), severe hypothermia sets in. Shivering is completely absent. The person loses all voluntary movement, and muscles become totally rigid. Blood pressure drops to very low levels. Breathing becomes extremely shallow or may be hard to detect. The heart can stop entirely.
A person in severe hypothermia can fall into a coma that closely mimics death. Their pulse may be undetectable, and they may show no visible signs of breathing. This is why rescue teams follow the principle that a hypothermic person is not considered dead until they are warm and dead. Resuscitation efforts continue until core temperature rises above 32°C.
Paradoxical Undressing and Terminal Burrowing
Two bizarre behaviors sometimes appear in the late stages of hypothermia. In paradoxical undressing, a severely hypothermic person removes their clothing, seemingly convinced they feel warm. This happens because blood vessels near the skin suddenly dilate, flooding cold skin with warm blood and creating a false sensation of heat.
Terminal burrowing is the other phenomenon. People in the final stages of hypothermia crawl into small, enclosed spaces: under a bed, behind furniture, into a closet. Researchers at the Icahn School of Medicine at Mount Sinai have described this as a primitive, involuntary response driven by the brain stem, similar to the burrowing behavior seen in hibernating animals. It appears to be an automatic protective mechanism that kicks in as higher brain functions shut down. Nearly all bodies found partially undressed in hypothermia cases were also found in these tucked-away positions.
Signs in Babies
Infants lose heat much faster than adults and can’t tell you they’re cold. The signs look different than in older children or adults. A hypothermic baby will have bright red, cold skin and unusually low energy. They may be floppy, quiet, or refuse to eat. Because babies can’t shiver effectively, the absence of shivering doesn’t mean they’re fine. Any combination of cold skin, redness, and lethargy in a baby exposed to cold temperatures is a serious warning sign.
Signs in Older Adults
Older adults are especially vulnerable to hypothermia, and the signs can be subtle enough to miss. Aging changes the body’s ability to sense and respond to cold, so an older person may not feel uncomfortably chilled even as their temperature drops. Early signs include cold hands and feet, a puffy or swollen face, pale skin, shivering, slurred speech, and unusual sleepiness, anger, or confusion.
What makes this population particularly at risk is the setting. Hypothermia in older adults doesn’t require a blizzard or a fall into icy water. Even mildly cool indoor temperatures, between 60 and 65°F, can cause hypothermia over time. If an older person lives alone in an under-heated home, the condition can develop gradually over hours or days. If exposure continues, symptoms progress to stiff, jerky limb movements, slow heartbeat and breathing, and loss of consciousness.
How Quickly Hypothermia Develops
The speed of onset depends on the conditions. Immersion in cold water can cause hypothermia in minutes because water pulls heat from the body roughly 25 times faster than air at the same temperature. In cold air, it typically takes longer, especially if the person is dry and somewhat sheltered. But wind, wet clothing, exhaustion, alcohol use, and lack of food all accelerate heat loss significantly.
Alcohol is a particularly deceptive risk factor. It dilates blood vessels near the skin, creating a feeling of warmth while actually speeding up core heat loss. A person drinking outdoors in cold weather may feel fine while their temperature is actively dropping.
What to Do if You Spot These Signs
If someone shows signs of hypothermia, the priority is stopping further heat loss. Get them out of the cold and into a warm, dry environment. Remove any wet clothing and cover them with blankets, coats, or whatever insulation is available. Focus warmth on the center of the body: chest, neck, head, and groin. Warm (not hot) drinks can help if the person is alert enough to swallow safely. Avoid applying direct heat like hot water or heating pads to the arms and legs, as this can push cold blood from the extremities toward the heart and actually lower core temperature further.
Handle the person gently, particularly if you suspect moderate or severe hypothermia. Rough movement can trigger irregular heart rhythms in a deeply cold heart. If the person is unconscious but breathing, keep them warm and horizontal while waiting for emergency help. If there’s no detectable pulse or breathing, CPR is appropriate while rewarming continues.