Cold stress on the job: spotting hypothermia and frostbite before they turn serious

Cold-weather work carries a hazard that's easy to underestimate because it doesn't feel dangerous until it's advanced: cold stress. Hypothermia and frostbite don't require arctic conditions — a wet, windblown worker can develop hypothermia at temperatures in the 40s or 50s — and the person in trouble is usually the last to recognize it. Knowing the signs, and the one that means "call 911," is what keeps a cold day from becoming a fatality.

Why cold is more dangerous than it feels

Your body fights to hold its core temperature, and once it starts losing that fight, judgment and coordination go first. Two multipliers make it worse: wind, which strips heat from exposed skin far faster than still air (the "feels-like" wind-chill temperature is the real one), and wetness, because water pulls heat from the body about 25 times faster than air. A worker soaked by rain, spray, or their own sweat is on a fast track to cold stress even in mild cold.

Hypothermia: watch for the "umbles"

Early hypothermia looks like this: uncontrollable shivering, cold and pale skin, fatigue, clumsiness, and confusion or slurred speech. A useful field cue is the "umbles" — stumbles, mumbles, fumbles, and grumbles. A coworker who is shivering, dropping tools, and not making sense is showing you early hypothermia, even if they insist they're fine.

The sign that means emergency: shivering stops. When a cold, confused worker stops shivering, it doesn't mean they're warming up — it means the body has given up trying to warm itself, and severe hypothermia has set in. Skin may turn bluish, breathing and pulse slow, and consciousness fades. Move them somewhere warm, remove wet clothing, wrap them in dry insulation including the head, handle them gently (rough handling can trigger cardiac arrest in severe cases), call 911, and give warm sweet non-alcoholic drinks only if they're fully alert.

Frostbite and trench foot

Frostbite is actual freezing of tissue — usually fingers, toes, nose, ears, cheeks. The skin goes numb and turns white, grayish-yellow, or waxy and firm. Do not rub it (that damages frozen tissue) and do not rewarm it if there's any chance it will refreeze, which is far worse. Get out of the cold and seek medical care.

Trench foot comes from prolonged wet and cold without freezing: numb, red or blotchy, swollen, painful feet. Dry and gradually warm the feet, change into dry socks, and get medical attention. Prevention is simple — keep feet dry.

Prevention in one line

Dress in wicking layers (not cotton), stay dry, protect head, hands, and feet, take warm-up breaks that get more frequent as conditions worsen, and use a buddy system so someone catches the "umbles" before they become an emergency. Our Cold Stress Prevention course covers wind chill, layering, work practices, and cold-injury response in full.