Explainer

The picture most people carry of hypothermia — deep snow, extreme cold — is the least common version. The conditions that produce most cases are wet, windy and moderately cool.

Why 40 degrees and raining is worse than 15 and dry

Water conducts heat away from the body far faster than air. Wet clothing loses most of its insulating value, and wind accelerates the loss further.

So a soaked hiker at 45 degrees in a breeze is losing heat faster than a dry one at 20 degrees in still air. That is the trap.

The progression

Mild. Shivering, cold extremities, reduced fine motor control. Fumbling with zips and buckles is an early and reliable sign.

Moderate. Shivering becomes violent then, notably, stops. Confusion, slurred speech, stumbling, poor judgement. The person may deny anything is wrong, and that denial is itself a symptom.

Severe. Shivering has ceased, consciousness is impaired, muscles are rigid. This is a medical emergency with a real mortality rate.

The stage most likely to be missed is moderate, because the affected person is the one making decisions and their judgement is what has degraded.

The response

Stop heat loss first: get out of wind and wet, remove wet layers, insulate from the ground — which conducts heat as effectively as water.

Add calories and warm sweet drinks if the person can swallow reliably. Alcohol makes it worse by dilating peripheral vessels.

Handle a severely hypothermic person gently and get help. Rough handling can trigger cardiac arrhythmia.

What prevents it

Layers that insulate when wet, a genuine wind and rain shell, spare dry insulation kept dry, calories, and turning around earlier than feels necessary.

And travelling with someone who will tell you that you are slurring, because you will not notice.

This article was researched and drafted with the assistance of AI tools and reviewed, fact-checked and edited by Leonidas Clark before publication. Rules vary by agency and unit; check the managing office before you go.